<PAGE>   1
 
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MARCH 3, 1999
 
                                                     REGISTRATION NO. 333-
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
                            ------------------------
 
                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------
 
                      ONESOURCE INFORMATION SERVICES, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
                            ------------------------
 
<TABLE>
<S>                                  <C>                                  <C>
              DELAWARE                               7375                              04-3204522
    (STATE OR OTHER JURISDICTION         (PRIMARY STANDARD INDUSTRIAL               (I.R.S. EMPLOYER
 OF INCORPORATION OR ORGANIZATION)       CLASSIFICATION CODE NUMBER)             IDENTIFICATION NUMBER)
</TABLE>
 
                            ------------------------
 
                            150 CAMBRIDGEPARK DRIVE
                              CAMBRIDGE, MA 02140
                                  617-441-7000
         (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING
            AREA CODE, OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)
                            ------------------------
 
           DANIEL J. SCHIMMEL, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                      ONESOURCE INFORMATION SERVICES, INC.
                            150 CAMBRIDGEPARK DRIVE
                              CAMBRIDGE, MA 02140
                                  617-441-7000
            (NAME, ADDRESS INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
                   INCLUDING AREA CODE, OF AGENT FOR SERVICE)
                            ------------------------
                                   COPIES TO:
 
<TABLE>
<S>                                                   <C>
               LAWRENCE S. WITTENBERG                                  KEVIN F. BLATCHFORD
           TESTA, HURWITZ & THIBEAULT, LLP                               SIDLEY & AUSTIN
                   125 HIGH STREET                                  ONE FIRST NATIONAL PLAZA
             BOSTON, MASSACHUSETTS 02110                             CHICAGO, ILLINOIS 60603
                 TEL: (617) 248-7000                                   TEL: (312) 853-7000
                 FAX: (617) 248-7100                                   FAX: (312) 853-7036
</TABLE>
 
     APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:  As soon
as practicable after the effective date hereof.
     If any of the securities being registered on this form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, check the following box.  [ ]
     If this form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, check the following box and
list the Securities Act registration statement number of the earlier effective
registration statement for the same offering.  [ ] _____________.
     If this form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ]____________.
     If this form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ] ____________.
     If delivery of the prospectus is expected to be made pursuant to Rule 434,
check the following box.  [X]
                            ------------------------
 
                        CALCULATION OF REGISTRATION FEE
 
<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------
      TITLE OF EACH CLASS OF                  PROPOSED MAXIMUM
    SECURITIES TO BE REGISTERED          AGGREGATE OFFERING PRICE(1)         AMOUNT OF REGISTRATION FEE(1)
-------------------------------------------------------------------------------------------------------------
<S>                                  <C>                                  <C>
Common stock.......................            $40,500,000.00                         $11,259.00
-------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------
</TABLE>
 
(1) Estimated solely to calculate the registration fee.
                            ------------------------
 
     THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933 OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
<PAGE>   2
 
THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. WE MAY
NOT SELL THESE SECURITIES UNTIL THE REGISTRATION STATEMENT FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER
TO SELL THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY THESE 
SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.
 
                SUBJECT TO COMPLETION, DATED             , 1999
 
PROSPECTUS
 
                                             SHARES
 
                              [ONE SOURCE LOGO]
 
                                 COMMON STOCK
 
     OneSource Information Services, Inc. is offering            shares of its
common stock and the selling stockholders are offering            shares of
OneSource's common stock owned by them. We will not receive any of the proceeds
from the selling stockholders' sale of their shares.
 
     This is our initial public offering and no public market currently exists
for our shares. We expect the initial public offering price to be between
$           and $           per share. We intend to apply for quotation of the
common stock on the Nasdaq National Market under the symbol "ONES."
 
     INVESTING IN OUR COMMON STOCK INVOLVES CERTAIN RISKS. FOR MORE INFORMATION,
SEE "RISK FACTORS" ON PAGE 7.
                          ---------------------------
 
     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES, OR DETERMINED THAT
THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.
 
<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------
                                                            PER SHARE              TOTAL
-----------------------------------------------------------------------------------------------
<S>                                                    <C>                  <C>
Public Offering Price................................  $                    $
Underwriting Discount................................  $                    $
Proceeds to OneSource Information Services, Inc......  $                    $
Proceeds to Selling Stockholders.....................  $                    $
-----------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------
</TABLE>
 
     The Underwriters may also purchase at the public offering price, less the
underwriting discount, up to            additional shares from the selling
stockholders within 30 days from the date of this prospectus to cover any
over-allotments.
 
     We expect that the shares of the common stock will be ready for delivery on
or about              , 1999.
 
WILLIAM BLAIR & COMPANY
                        U.S. BANCORP PIPER JAFFRAY INC.
                                                    ADAMS, HARKNESS & HILL, INC.
 
               The date of this prospectus is              , 1999
<PAGE>   3
 
     [The inside front cover depicts four computer screen shots of the OneSource
Business Browser. The heading on the page is "Ready-To-Use Business
Information." The top three computer screen shots depict the Global Business
Browser, the European Business Browser, and the UK Business Browser. The fourth
computer screen shot depicts Market Forecasts and contains a chart graphic.
There are four ellipses on the page that briefly describe the potential uses of
the business information contained in the Business Browser products, including:
"Profile a Company"; "Prospect for New Customers"; "Track Competitors"; and
"Research an Industry". The OneSource logo is in the lower right hand corner of
the page.]
 
                          ---------------------------
 
     OneSource(TM), Business Browser(TM), OneSource Business Browser(TM),
Business Browser AppLink(TM), AppLink(TM), and the OneSource logo are our
trademarks. Other trademarks and tradenames in this prospectus are the property
of their respective owners.

                          ---------------------------
 
     Unless the context otherwise requires, any reference to "OneSource" in this
prospectus means OneSource Information Services, Inc. and its subsidiary. Unless
otherwise indicated, all information contained in this prospectus:
 
        - reflects the merger on February 26, 1999 of OneSource Information
          Services, Inc. into its parent, OneSource Holding Corporation, and the
          name change of OneSource Holding Corporation to OneSource Information
          Services, Inc.
 
        - assumes no exercise of the Underwriters' over-allotment option
 
        - reflects the reclassification (prior to the completion of the
          offering) of each share of Class P common stock into one share of
          common stock plus            additional shares of common stock
          (determined by dividing the preference amount for each share of Class
          P common stock by the assumed initial public offering price)

                          ---------------------------
 
     This prospectus contains certain forward-looking statements that involve
substantial risks and uncertainties. When used in this prospectus, the words
"anticipate," "believe," "estimate," "intend" and "expect" and similar
expressions are intended to identify such forward-looking statements. Our actual
results, performance or achievements could differ materially from the results
expressed in or implied by these forward-looking statements. Factors that could
cause or contribute to such differences include those discussed in "Risk
Factors."
                                        2
<PAGE>   4
 
                               PROSPECTUS SUMMARY
 
     This summary highlights information contained elsewhere in this prospectus.
It is not complete and does not contain all of the information that you should
consider before investing in our common stock. You should read the entire
prospectus carefully.
 
                                  THE COMPANY
 
     OneSource provides Web-based business and financial information to
professionals who need quick access to reliable corporate, industry and market
intelligence. Our Business Browser product line integrates comprehensive and
up-to-date business and financial information on over one million public and
private companies from more than 25 information providers drawing upon over
2,500 sources of content. These sources include both textual information, such
as news, trade press, SEC filings, executive biographies and analyst reports,
and numeric information, such as company financial results, stock quotes and
industry statistics. Our customers access this information over the Internet
using standard Web browsers at a fixed annual subscription price.
 
     According to an industry source, the market for all Web-based and on-line
business information services was $24.8 billion in 1997 and is projected to grow
to $39.8 billion in 2002, reflecting a compound annual growth rate of 9.9%.
According to this industry source, the primary market segment in which OneSource
participates--Web-based and on-line financial news, current awareness and
research services--was $5.4 billion in 1997 and is projected to grow to $9.8
billion in 2002, reflecting a compound annual growth rate of 12.6%. Recent
industry growth has been driven by corporations and other enterprises
recognizing that productivity and competitiveness depend on extensive knowledge
of external information, including information about industries, customers,
competitors, prospects, business trends, breaking news and market data.
 
     OneSource focuses on the functional uses of the business and financial
information it delivers. The Business Browser product line has been designed for
use not only by traditional users of business information, but also throughout
an organization, including sales, marketing, finance and management
professionals. We apply our knowledge of how business professionals use
information to transform raw, disparate data into meaningful, actionable
information. We focus on integrating and presenting information so that
interpretation, manipulation and analysis can be performed more easily by the
end user. Because our products are based on standard Web technology, our
customers require minimal installation and systems support, and users, after
minimal training, have full access to the products at any time from anywhere via
the Internet.
 
     Our products are designed to address information needs of leading
professional and financial services firms, technology companies and other large
organizations. Representative customers include American Express, Bain &
Company, BankAmerica, Boeing, British Telecom, Deloitte & Touche, Ernst & Young,
Harvard Business School, KPMG Peat Marwick, MCI/WorldCom, Merrill Lynch, Oracle
and SAP.
 
     OneSource's fixed annual pricing strategy is designed to be particularly
attractive to large organizations. The annual subscription price for the
Business Browser product line declines on a per-user basis as the total number
of users increases. The fixed-price model encourages professionals to use the
products as needed without concern with additional, usage-based charges,
                                        3
<PAGE>   5
 
and a declining marginal price per user encourages customers to distribute the
products widely throughout their organizations.
 
     At December 31, 1998, 445 organizations subscribed to our Web-based
Business Browser product line, up from 233 at December 31, 1997. On average, our
customers for Web-based products at December 31, 1998 had an annualized contract
value of $58,248 per customer, compared to $38,512 per customer at December 31,
1997. The annualized value of Business Browser customer contracts was $25.9
million at December 31, 1998, having grown from $9.0 million at the end of 1997.
Of this $25.9 million, $14.2 million was attributable to those customers that
were under contract at both December 31, 1997 and 1998. The renewal rate of the
Business Browser product line for 1998 was 90% calculated on a dollar basis. For
more information regarding annualized contract value, see "Management's
Discussion and Analysis of Financial Condition and Results of Operations."
 
     Our goal is to become a leading Web-based provider of business and
financial information to professionals worldwide. Our strategy to accomplish
this objective includes:
 
        - focusing on the information needs of professionals in large
          organizations
 
        - expanding our customer base through our sales and marketing efforts
 
        - leveraging our existing customer base by expanding the number of users
          per customer and upgrading those customers to new or enhanced products
 
        - continually expanding the content and functionality of our products
          and designing additional products
 
        - selectively seeking possible strategic acquisitions and alliances
 
                                  THE OFFERING
 
<TABLE>
<S>                                        <C>
Shares offered by OneSource..............
Shares offered by the selling
  stockholders...........................  
Shares outstanding immediately after the
  offering...............................        (1)
Use of proceeds..........................  Repayment of outstanding debt, repurchase
                                           of certain common stock in connection
                                           with the reclassification, payments to
                                           terminate management fee arrangements and
                                           general corporate purposes, including
                                           working capital and possibly to acquire
                                           or invest in complementary businesses,
                                           products or technologies
Proposed Nasdaq National Market symbol...  ONES
</TABLE>
 
------------
(1) Based on shares of common stock outstanding as of           , 1999. Excludes
                shares of common stock issuable upon the exercise of stock
    options and warrants outstanding on           , 1999 with a weighted average
    exercise price of $        and an aggregate of     shares reserved for
    future stock option grants and purchases under our equity compensation
    plans. For more information, see "Description of Capital Stock,"
    "Management--Equity Plans" and Notes 6, 7 and 8 to the Consolidated
    Financial Statements.
                                        4
<PAGE>   6
 
                      SUMMARY CONSOLIDATED FINANCIAL DATA
      (IN THOUSANDS, EXCEPT PER SHARE, SHARE AND NUMBER OF CUSTOMERS DATA)
 
<TABLE>
<CAPTION>
                                                           YEAR ENDED DECEMBER 31,
                                                        -----------------------------
                                                         1996       1997       1998
                                                        -------    -------    -------
<S>                                                     <C>        <C>        <C>
STATEMENT OF OPERATIONS DATA:
Web-based product revenues............................  $    15    $ 3,312    $16,058
CD Rom product revenues(1)............................   30,419     27,072     14,370
                                                        -------    -------    -------
  Total revenues......................................   30,434     30,384     30,428
                                                        =======    =======    =======
Gross profit..........................................   17,895     17,539     16,773
Operating expenses....................................   19,488     18,943     21,737
                                                        -------    -------    -------
Loss from operations..................................   (1,593)    (1,404)    (4,964)
Interest income (expense), net........................     (733)      (930)      (595)
Gain on sale of product line..........................       --        501     12,797
                                                        -------    -------    -------
Income (loss) before income taxes and extraordinary
  gain................................................   (2,326)    (1,833)     7,238
                                                        =======    =======    =======
Net income (loss).....................................  $(1,933)   $(1,833)   $ 6,988
                                                        =======    =======    =======
Unaudited pro forma earnings per share:(2)
  Basic...............................................                        $
  Diluted.............................................                        $
  Weighted average common shares outstanding:
     Basic............................................
     Diluted..........................................
</TABLE>
 
<TABLE>
<CAPTION>
                                                                    DECEMBER 31, 1998
                                                              ------------------------------
                                                                                UNAUDITED
                                                                                PRO FORMA
                                                                 ACTUAL       AS ADJUSTED(3)
                                                              ------------    --------------
<S>                                                           <C>             <C>
BALANCE SHEET DATA:
Cash and cash equivalents...................................    $ 8,665           $
Working capital (deficit)...................................     (2,118)
Total assets................................................     27,646
Total debt (including capital lease obligations)............      6,936               704
Deferred revenues...........................................     18,022            18,022
Total stockholders' equity (deficit)........................     (6,311)
</TABLE>
 
<TABLE>
<CAPTION>
                                                                DECEMBER 31,
                                                        -----------------------------
                                                         1996       1997       1998
                                                        -------    -------    -------
<S>                                                     <C>        <C>        <C>
OTHER DATA FOR WEB-BASED PRODUCTS (UNAUDITED):
Annualized contract value(4)..........................  $   412    $ 8,973    $25,920
Number of customers...................................       11        233        445
Average annualized contract value per customer........  $  37.4    $  38.5    $  58.2
</TABLE>
 
------------
(1) In 1997 and 1998, OneSource divested certain CD Rom product lines. Revenues
    attributable to these divested product lines, which are included in the
    statement of operations data through the divestiture date, were $6,415,000,
    $6,630,000 and $2,612,000 in the years ended December 31, 1996, 1997 and
    1998, respectively.
 
(2) Unaudited pro forma basic and diluted earnings per share of common stock for
    the year ended December 31, 1998 have been calculated based on net income
    attributable to all classes of common stock and assuming the
    reclassification of OneSource's
                                        5
<PAGE>   7
 
    Class P common stock prior to completion of this offering as if it had
    occurred at January 1, 1998. In the reclassification, each share of Class P
    common stock will be reclassified into one share of common stock plus an
    additional number of shares of common stock (determined by dividing the
    preference amount for such share by the assumed initial public offering
    price of $        per share). As described in "Use of Proceeds", OneSource
    intends to use a portion of its net proceeds to repay a $6.2 million note
    due to Lotus Development Corporation and to pay $1.0 million to terminate
    certain management fee arrangements. Accordingly, had the note repayment and
    the management fee termination occurred at January 1, 1998, unaudited
    supplemental pro forma basic and diluted earnings per share for the year
    ended December 31, 1998 would be $        and $        , respectively. Such
    amounts reflect the elimination of annual interest expense on the note of
    $0.5 million and the elimination of annual management fees of $0.2 million,
    and the issuance of             shares of common stock at the assumed
    initial public offering price of $        per share necessary to fund the
    note repayment and management fee termination.
 
(3) This column shows the numbers in the "Actual" column as adjusted to give
    effect to:
 
    - the reclassification of each share of OneSource's Class P common stock
      prior to the completion of this offering into one share of common stock
      plus an additional number of shares of common stock (determined by
      dividing the preference amount as of December 31, 1998 for such share by
      the assumed initial public offering price of $        per share);
 
    - the sale of       shares of common stock by OneSource in this offering at
    the assumed initial public offering price of $
     per share, as if the sale had been completed on December 31, 1998;
 
    - the use of a portion of the estimated net proceeds to OneSource from this
      offering to pay off the note due to Lotus Development Corporation for $6.2
      million plus accrued interest as of December 31, 1998 of $0.5 million;
 
    - the use of a portion of the estimated net proceeds to OneSource from this
      offering to repurchase for $        million         shares of common stock
      which were issued to holders of Class P common stock in satisfaction of
      their preference amount; and
 
    - the use of a portion of the estimated net proceeds to OneSource from this
      offering to pay $1.0 million to terminate certain management fee
      arrangements.
 
    For more information, see "Reclassification," "Use of Proceeds" and
"Capitalization."
 
(4) Annualized contract value represents the invoiced fees for one month for all
    customer contracts for Web-based products in effect at the measurement date,
    multiplied by 12, without regard to the actual remaining duration of such
    contracts. At December 31, 1996, 1997 and 1998, annualized contract value
    was calculated by multiplying the total amount of fees invoiced for one
    month and included in deferred revenues for all customer contracts for
    Web-based products at December 31, 1996, 1997 and 1998 of $34,300, $747,750
    and $2,160,000, respectively, by 12. For more information regarding
    annualized contract value, see "Management's Discussion and Analysis of
    Financial Condition and Results of Operations."
 
                            ------------------------
 
     OneSource was incorporated in Delaware on July 21, 1993 under the name
Datext Holding Corporation. On February 26, 1999, OneSource Information
Services, Inc. merged into its parent, OneSource Holding Corporation, and the
name of the combined company was changed to OneSource Information Services, Inc.
Our principal executive offices are located at 150 CambridgePark Drive,
Cambridge, MA 02140, and our telephone number is (617) 441-7000.

                                        6
<PAGE>   8
 
                                  RISK FACTORS
 
     You should consider carefully the risks described below before you decide
to buy our common stock. The risks and uncertainties described below are not the
only ones we face. Additional risks and uncertainties that we do not presently
know about or that we currently believe are immaterial may also adversely impact
our business operations.
 
     If any of the following risks actually occur, our business, financial
condition or results of operations would likely suffer. In such case, the
trading price of our common stock could fall, and you may lose all or part of
the money you paid to buy our common stock.
 
     This prospectus also contains forward-looking statements that involve risks
and uncertainties. Our actual results could differ significantly from those
anticipated in these forward-looking statements as a result of certain factors,
including the risks we face, as more fully described below in this section and
elsewhere in this prospectus.
 
OUR BUSINESS BROWSER PRODUCTS HAVE NOT BEEN PROFITABLE
 
     We began operations as an independent company in 1993. We began to migrate
our business to the Web from CD Rom-based products in early 1996, and launched
the Web-based Business Browser product line in December 1996. Our prospects must
be considered in light of the risks, expenses and difficulties frequently
encountered by companies transitioning to a new product line, particularly
companies in the new and rapidly evolving market for Internet and Web-based
business information products. We incurred losses from operations of
approximately $1.6 million in 1996, $1.4 million in 1997 and $5.0 million in
1998. In addition, we have not reached the critical mass of users of Web-based
products which we believe is necessary to leverage effectively our
infrastructure expenses and become profitable. As of December 31, 1998, we had
an accumulated deficit of $10.4 million.
 
WE RELY PRIMARILY ON OUR BUSINESS BROWSER PRODUCT LINE
 
     Subscription revenues from our Business Browser product line accounted for
83% of our total annualized contract value at the end of 1998 and 29% at the end
of 1997. We are currently phasing out CD Rom products that are not part of the
Business Browser product line. As a result, our future financial condition will
depend heavily on the success or failure of our Business Browser product line.
Business Browser products were introduced in December 1996 and it is difficult
to predict demand and market acceptance for these products in the new and
rapidly evolving Web-based business information services market. If the demand
for Business Browser products does not grow, whether due to competition, lack of
market acceptance, failure of Internet or Web use to grow in general,
technological change or other factors, our business would suffer significantly.
 
WE FACE INTENSE COMPETITION
 
     The business information services industry is intensely competitive. We
face direct or indirect competition from the following types of companies:
 
        - large, well-established business and financial information providers
          such as Dow Jones, Dialog, Lexis-Nexis, Pearson, Reuters, Thomson,
          Primark and McGraw-Hill
 
                                        7
<PAGE>   9
 
        - on-line information services or Websites targeted to specific markets
          or applications, such as NewsEdge, Factset and Bloomberg
 
        - providers of sales, marketing and credit information such as Dun &
          Bradstreet
 
        - Web retrieval, Web "portal" companies and other free or low-cost mass
          market on-line services such as Excite, Infoseek, Lycos, Yahoo! and
          AOL/Netscape
 
     Many of our existing competitors, as well as a number of prospective
competitors, have longer operating histories, greater name recognition, larger
customer bases and significantly greater financial, technical and marketing
resources than we do. As a result, they may be able to respond more quickly to
new or emerging technologies and changes in user requirements, or to devote
greater resources to the development, promotion and sale of their products than
we can. Such competitors may be able to undertake more extensive marketing
campaigns, adopt more aggressive pricing policies and make more attractive
offers to potential employees, customers and information providers. Our
competitors also may develop products that are equal or superior to our products
or that achieve greater market acceptance than our products.
 
     Certain of our competitors offer financial and business information free of
charge with the goal of achieving high enough usage to facilitate the sale of
substantial amounts of advertising. To the extent these types of competitors
offer products free of charge that are similar to ours, it would have a material
adverse impact on our business, financial condition and results of operations.
In addition, there are relatively low barriers to entry to the Web-based
information market and we may face additional competition from new entrants. We
also expect that competition may increase as a result of industry consolidation.
It is possible that new competitors may emerge and rapidly acquire significant
market share. Increased competition is likely to result in price reductions,
reduced gross margins and loss of market share. Any of these would have a
material adverse effect on our business, financial condition and results of
operations.
 
WE DEPEND ENTIRELY ON OUR INFORMATION PROVIDERS FOR CONTENT
 
     We do not own or create the original content distributed through our
products. We depend on information providers to supply information and data
feeds to us on a timely basis. Our products could experience interruptions due
to any failure or delay in the transmission or receipt of this information.
 
     Many of our information providers compete with one another and, in some
cases, with us, for users. Business decisions made by our information providers
could adversely affect the availability or pricing of their information to us.
Any increase in the fees we negotiate with our information providers could have
an adverse effect on our results of operations.
 
     Our arrangements with our information providers generally extend for
one-year periods, which automatically renew unless terminated by notice given at
least three months prior to the end of the term. In the event of a breach by us,
the contracts can be terminated on relatively short notice. An information
provider may be difficult to replace and the loss of one or more significant
information providers could decrease the quality, quantity or mix of the
information distributed through our products. This could make our products less
competitive. If information providers terminate their relationships with us, our
business and delivery of our products may be disrupted. This could result in a
loss of customers or requests for refunds.
 
                                        8
<PAGE>   10
 
IF OUR WEBSITE SERVICE IS DISRUPTED, OUR BUSINESS WOULD BE ADVERSELY AFFECTED
 
     Our on-line site is located at a dedicated hosting facility and we do not
currently have a shadow site fully equivalent to the live on-line site. Any
damage to the hosting facility or the equipment there, such as damage by fire or
power loss, or loss of telecommunications could disrupt the delivery of our
products. In addition, our users depend on Internet service providers, on-line
service providers and other Website operators for access to our products. Each
of them has experienced significant outages in the past, and could experience
outages, delays and other difficulties due to system failures unrelated to our
on-line architecture. These types of occurrences could cause users to perceive
our products as not functioning properly and therefore cause them to use other
methods to obtain their business and financial information.
 
     The number of Business Browser users has increased since its introduction
in December 1996 and we are seeking to further increase our user base. This has
led to increased usage and increased demands on our on-line architecture. Any
downtime or slow response times may damage our reputation and make it more
difficult to attract new users.
 
OUR MARKET IS NEW AND RAPIDLY EVOLVING
 
     The market for Web-based distribution of electronic business and financial
information has only recently begun to develop and it is rapidly evolving. This
makes it difficult to predict demand and market acceptance for our products. We
cannot guarantee that the market for our products will grow or that our products
will become widely accepted. If the market for our products does not develop as
quickly as we expect or if our products are not accepted by customers, our
future financial results will be adversely affected. A significant increase in
the number of customers and development of new product offerings could also
require the expenditure of significant amounts of money, time and other
resources. This could strain our personnel and financial resources.
 
WE DEPEND ON CONTINUED GROWTH IN INTERNET USE
 
     Our business would be adversely affected if the number of professionals
using the Web does not continue to grow. This growth may be inhibited by a
number of factors, such as:
 
        - inadequate network infrastructure
 
        - inconsistent quality of service
 
        - lack of cost-effective, high-speed service
 
        - security concerns
 
     Even if Web use grows, the Internet infrastructure may not be able to
support adequately future growth and its reliability and quality of service may
suffer. In addition, numerous Websites have experienced service interruptions
due to outages and other delays occurring internally and throughout the Internet
network infrastructure. If these outages or delays occur frequently in the
future, Web usage, as well as usage of our products, could grow more slowly or
decline.
 
GOVERNMENT REGULATION AND LEGAL UNCERTAINTIES RELATING TO THE WEB COULD HURT OUR
BUSINESS
 
     Currently, there are few laws or regulations that specifically regulate
communications or commerce on the Web. However, laws and regulations may be
adopted that address issues such
 
                                        9
<PAGE>   11
 
as user privacy, pricing and the characteristics and quality of products and
services. For example, the Telecommunications Act sought to prohibit the
transmission of certain types of information and content over the Web. In
addition, several telecommunications companies have petitioned the Federal
Communications Commission to regulate Internet and on-line service providers in
a manner similar to long distance telephone carriers and to impose access fees
on such providers. This could increase the cost of transmitting data over the
Internet. Moreover, it may take years to determine the extent to which existing
laws relating to issues such as property ownership, libel and personal privacy
apply to the Web. Finally, state tax laws and regulations relating to the
provision of products and services over the Internet are still developing. If
individual states impose taxes on products and services provided over the Web,
the cost of our products may increase and we may not be able to increase the
price we charge for our products to cover these costs. Any new laws or
regulations or new interpretations of existing laws and regulations relating to
the Web could adversely affect our business.
 
WE RELY ON OUR INTELLECTUAL PROPERTY
 
     We believe that our success depends, in large part, on protecting our
intellectual property in the United States and in foreign countries. Other than
certain trademarks, most of our intellectual property consists of proprietary or
confidential information that is not subject to patent or similar protection.
Competitors may independently develop similar or superior products, software or
business models.
 
     We cannot guarantee that we will be able to protect our intellectual
property. There is no way to assure that unauthorized third parties will not try
to copy our products or business model or use our confidential information to
develop competing products. Legal standards relating to the validity,
enforceability and scope of protection of certain proprietary rights in
Internet-related businesses are uncertain and still evolving. As a result, we
cannot predict the future viability or value of our proprietary rights and those
of other companies within the industry. We also cannot guarantee that our
business activities and products will not infringe upon the proprietary rights
of others, or that other parties will not assert infringement claims against us.
Any such claims and any resulting litigation, should it occur, could subject us
to significant liability for damages and could result in invalidation of our
proprietary rights. Even if we eventually won any such litigation, it could be
time-consuming and expensive to defend, and could result in the diversion of our
management's time and attention.
 
WE COULD BE SUBJECT TO LEGAL LIABILITY FOR DISTRIBUTING INFORMATION ON OUR
WEBSITE
 
     We may be subjected to claims based on negligence or other theories
relating to the information we distribute. Similarly, we may be subjected to
claims for defamation or copyright or trademark infringement relating to the
information we provide in our products. These types of claims have been brought,
sometimes successfully, against on-line services as well as print publications
in the past. We also could be subjected to claims based upon the content that is
accessible from our products through links to other Websites. These types of
claims could be time-consuming and expensive to defend, and could result in the
diversion of our management's time and attention. In addition, if our products
provide faulty or inaccurate information, or fail to provide all the information
a user expects, we could be subject to legal liability. Our insurance and
contractual provisions with users and information providers may not protect us
against these types of claims.
 
                                       10
<PAGE>   12
 
OUR PRODUCTS COULD CONTAIN SOFTWARE DEFECTS
 
     Complex software like the software we develop for our products may contain
errors or defects, especially when first implemented, that may be very costly to
correct. Defects or errors also could result in downtime and our business could
suffer significantly from potential adverse customer reaction, negative
publicity and harm to our reputation.
 
WE MAY EXPERIENCE SIGNIFICANT FLUCTUATIONS IN OUR QUARTERLY RESULTS
 
     Our quarterly revenues, gross profits and results of operations have
fluctuated significantly in the past and we expect them to continue to fluctuate
significantly in the future. In addition, we believe that an important measure
of our business is the annualized contract value at the end of each period,
which also may fluctuate. Causes of such fluctuations have included and may
include, among other factors:
 
        - changes in demand for our products
 
        - the dollar value and timing of both new and renewal subscriptions
 
        - competition (particularly price competition)
 
        - changes in operating expenses
 
        - technical difficulties or system downtime affecting our products on
          the Web generally
 
        - economic conditions specific to the Web, as well as general economic
          conditions
 
        - consolidation of our customers
 
     In addition, a substantial portion of our expenses, including certain
product development and selling and marketing expenses, must be incurred in
advance of revenue generation. If our projected revenue does not meet our
expectations, then we may have an operating loss in a particular quarter.
 
     Any one or more of these factors could affect our business, financial
condition and results of operations, and this makes the prediction of results of
operations on a quarterly basis unreliable. As a result, we believe that
period-to-period comparisons of our historical results of operations and
annualized contract values are not necessarily meaningful and that you should
not rely on them as an indication for future performance. Also, due to these and
other factors, it is possible that our quarterly results of operations
(including the annualized contract value) may be below the expectations of
public market analysts and investors. If this happens, the price of our common
stock would likely decrease.
 
WE DEPEND ON KEY PERSONNEL
 
     Our future success depends on the continued services of a number of key
employees, including Daniel J. Schimmel, our President and Chief Executive
Officer, James A. Becker, our Vice President, Global Strategic Web Applications
Team, Philip J. Garlick, our Vice President, Global Enterprise Sales and
Marketing, Mark C. VanDine, our Vice President, Engineering and Roy D. Landon,
our Vice President, Finance and Administration. We also depend on a limited
number of engineers to monitor the performance and availability of our complex
network and to perform the necessary updates and repairs. We do not have
employment contracts with our key personnel. If any of our key employees leave,
the loss of their technological knowledge and industry expertise would seriously
impede the development of new products and services and our
 
                                       11
<PAGE>   13
 
ability to manage our business. The loss of one or a group of our key employees
could adversely affect our future financial results.
 
THERE IS INTENSE COMPETITION FOR QUALIFIED PERSONNEL
 
     Our future performance also depends upon our ability to attract and retain
highly-qualified technical, sales and managerial personnel. Qualified personnel
are in great demand throughout the software and Internet industries and there is
intense competition for such personnel. In addition, competition for qualified
personnel may lead to increased costs for such personnel. If we do not succeed
in retaining our personnel or in attracting new employees, our business could
suffer significantly.
 
WE ARE SUBJECT TO RISKS OF OPERATING INTERNATIONALLY
 
     Revenue from customers located outside North America accounted for 23% in
1998, 20% in 1997 and 17% in 1996 of our total revenue for such years. Over
time, we expect revenue from international operations, principally in Europe, to
increase as a percentage of our total revenue. As a result, we may be exposed to
a number of risks customary for international operations, including:
 
        - difficulties relating to managing an international sales force
 
        - the burdens of complying with a wide variety of foreign laws
 
        - the uncertainty of laws and enforcement in certain countries relating
          to the protection of intellectual property
 
        - multiple and possibly overlapping tax structures
 
        - economic or political changes in international markets
 
        - currency and exchange rate fluctuations
 
        - adverse tax consequences of returning any earnings of our foreign
          operations back to the United States
 
     To date, we have not used risk management techniques or "hedged" the risks
associated with fluctuations in foreign exchange rates.
 
WE ARE SUBJECT TO RISKS ASSOCIATED WITH YEAR 2000 PROBLEMS
 
     Many existing computer systems and software products do not properly
recognize dates after December 31, 1999. This "Year 2000" problem could result
in miscalculations, data corruption, system failures or disruptions of
operations. We are subject to potential Year 2000 problems affecting
telecommunication services, customers, our products, our internal systems and
the systems of our hosting facility and our information providers, any of which
could have a material adverse effect on our business, financial condition and
results of operations. We also have identified certain third-party software as
non-compliant and certain internal systems need to be addressed as part of our
relocation in June 1999. For more information, see "Management's Discussion and
Analysis of Financial Condition and Results of Operations--Year 2000 Readiness
Disclosure Statement." Furthermore, as we approach the Year 2000, customers may
be forced to devote greater resources to comply with Year 2000 requirements and
as a result purchase fewer products from us, which would have an adverse effect
on our net revenues.
 
                                       12
<PAGE>   14
 
OUR EXISTING OFFICERS AND DIRECTORS WILL CONTINUE TO CONTROL ONESOURCE
 
     Following this offering, our officers and directors, together with entities
affiliated with them, will beneficially own approximately      % of our
outstanding shares of common stock (     % if the over-allotment option is
exercised in full). As a result, these stockholders acting together will be able
to take any of the following actions without the approval of our public
stockholders:
 
        - elect our directors
 
        - amend our charter or approve a merger, sale of assets or other major
          corporate transaction
 
        - defeat any non-negotiated takeover attempt that may be beneficial to
          our public stockholders
 
        - otherwise control the outcome of all matters submitted for a
          stockholder vote
 
THE OFFERING WILL BENEFIT SELLING STOCKHOLDERS
 
     The selling stockholders will receive substantial proceeds and certain
other benefits in connection with this offering. In addition, a selling
stockholder and an affiliate of another selling stockholder will each receive a
payment of $0.5 million out of OneSource's net proceeds to terminate a
management fee arrangement. For more information, see "Certain Transactions."
The offering will also establish a public market for the common stock and
provide significantly increased liquidity to our existing stockholders and
optionholders.
 
THERE IS NO PRIOR TRADING MARKET FOR OUR COMMON STOCK
 
     Before this offering, there was no public market for our common stock. We
and the underwriters have determined the initial public offering price of our
common stock based on negotiations between us concerning the proper valuation of
our common stock. Nevertheless, after this offering, you may not be able to
resell your shares at or above the initial public offering price due to a number
of factors, including:
 
        - actual or anticipated fluctuations in our operating results or
          annualized contract values
 
        - changes in expectations as to our future financial performance
 
        - changes in securities analysts' financial estimates
 
        - the operating and stock price performance of our competitors and other
          comparable companies
 
     In addition, the stock market in general, and the stocks of Web-based
businesses in particular, have experienced extreme volatility that often has
been unrelated to the operating performance of particular companies. These broad
market and industry fluctuations may adversely affect the trading price of our
common stock, regardless of our actual operating performance. You should read
the "Underwriting" section for a more complete discussion of the factors that
the underwriters and we considered in determining the initial public offering
price.
 
OTHER SHARES MAY BE SOLD IN THE FUTURE
 
     After this offering, we will have                 shares of common stock
outstanding and will have reserved an additional                 shares of
common stock for issuance pursuant to our stock option and purchase plans and
outstanding warrants. We intend to register for resale the shares of common
stock reserved for issuance under our stock option and stock purchase plans
approximately 180 days after the date of this prospectus. The federal securities
laws impose
 
                                       13
<PAGE>   15
 
certain restrictions on the ability of certain stockholders to resell their
shares. In addition, our officers and directors have agreed not to sell their
shares for a period of 180 days after the date of this prospectus.
 
     If a large number of our shares of common stock are sold following this
offering, the price of our common stock would likely decrease.
 
PURCHASERS WILL INCUR IMMEDIATE AND SUBSTANTIAL DILUTION
 
     The initial public offering price of our common stock is substantially
higher than the resulting net tangible book value per share of the outstanding
common stock after the offering. Accordingly, if you purchase any shares of
common stock in this offering you will incur immediate dilution of approximately
$           in the net tangible book value per share of the common stock from
the price you pay for our common stock.
 
OUR ANTI-TAKEOVER PROVISIONS MAY HAVE ADVERSE EFFECTS
 
     Our Restated Certificate of Incorporation and Amended and Restated By-laws
contain anti-takeover provisions that could have the effect of delaying or
preventing changes in our management, even if such changes would benefit our
public stockholders. For example, following the closing of this offering, the
Board of Directors may issue up to one million shares of preferred stock without
any further vote or action by the stockholders. The preferred stock could have
voting, liquidation, dividend and other rights superior to those of the common
stock, and, therefore, any issuance of preferred stock could adversely affect
your rights as a common stockholder. These factors could cause the market price
of the common stock to decrease.
 
WE DO NOT EXPECT TO PAY DIVIDENDS
 
     We do not expect to pay cash dividends on our common stock in the
foreseeable future.
 
                                RECLASSIFICATION
 
     Prior to the consummation of this offering, OneSource will reclassify all
of its outstanding shares of capital stock into a single class of common stock
and will authorize a single class of undesignated preferred stock. Each share of
Class P common stock will be reclassified into shares of common stock. Each
share of Class P common stock is entitled to a payment upon any distribution by
OneSource to holders of its capital stock in an amount equal to the original
cost of such share plus a preferential amount which accrues on a daily basis at
a rate of 12% per annum on such cost, compounded quarterly. As of              ,
1999, the preference amount of the outstanding Class P common stock will be
$           per share, based on an original cost per share of $           for an
aggregate preference of $           million. In connection with the
reclassification, each outstanding share of Class P common stock will be
reclassified into one share of common stock plus an additional number of shares
of common stock determined by dividing the applicable preference amount for such
share by the value of a share of common stock based on the initial public
offering price in the offering. Based on an assumed initial public offering
price of $           per share, an aggregate of            shares of common
stock will be issued upon the reclassification of all shares of Class P common
stock. Fractional shares otherwise issuable will be rounded down to the nearest
whole number. OneSource intends to repurchase the shares of common stock issued
with respect to the preference amount at the initial public offering price upon
completion of this offering. For more information, see "Use of Proceeds."
 
                                       14
<PAGE>   16
 
                                USE OF PROCEEDS
 
     We estimate our net proceeds from the issuance and sale of the
                shares of common stock being offered by OneSource hereby to be
approximately $           million, at an assumed initial public offering price
of $     per share, after deducting the estimated underwriting discount and
offering expenses. We will not receive any proceeds from the sale of the common
stock by the selling stockholders.
 
     The principal purposes of this offering are to repay debt, repurchase
certain shares of common stock in connection with the reclassification,
terminate certain management fee arrangements, obtain working capital, establish
a public market for our common stock, increase our visibility in the
marketplace, facilitate future access to public capital markets and provide
liquidity to existing stockholders and optionholders. We intend to use
approximately $6.7 million of the net proceeds to us to repay principal and
interest on a note issued by OneSource to Lotus Development Corporation in
connection with the purchase of OneSource's business from Lotus in 1993. The
note bears interest at the rate of 8% per year and is due September 8, 2000,
unless accelerated upon certain events. The completion of this offering would
require OneSource to repay a significant portion of the note if we do not repay
it in full. We also intend to use approximately $           million to
repurchase            shares of common stock issued to holders of Class P common
stock in the reclassification in satisfaction of their preference amount. For
more information, see "Reclassification." In addition, we intend to pay $0.5
million to each of William Blair Venture Partners III Limited Partnership and an
affiliate of Information Partners Capital Fund, L.P. to terminate certain
management fee arrangements. For more information, see "Certain Transactions."
 
     We intend to use the remaining net proceeds for general corporate purposes,
including working capital, and we may also use a portion of the net proceeds to
acquire or invest in complementary businesses or products or to obtain the right
to use complementary technologies. We have no specific understandings,
commitments or agreements with respect to any such acquisition or investment.
Pending such uses, our remaining net proceeds of the offering will be invested
in short-term, interest-bearing, investment-grade securities, certificates of
deposit or direct or guaranteed obligations of the United States.
 
                                DIVIDEND POLICY
 
     We have never paid any cash dividends on our common stock and do not
anticipate paying any cash dividends in the foreseeable future.
 
                                       15
<PAGE>   17
 
                                 CAPITALIZATION
 
     The left-hand column in the following table sets forth OneSource's
capitalization as of December 31, 1998. The middle column gives pro forma effect
to the reclassification of each outstanding share of OneSource's Class P common
stock into one share of common stock plus an additional number of shares of
common stock (determined by dividing the applicable preference amount as of
December 31, 1998 for such share by the value of a share of common stock based
on the assumed initial public offering price of $           per share) and the
filing of our Restated Certificate of Incorporation, each prior to the
completion of this offering. The right-hand column sets forth OneSource's pro
forma capitalization as of December 31, 1998, as further adjusted to reflect the
sale of                 shares of common stock by OneSource in this offering
(based on an assumed initial public offering price of $     per share), the use
of a portion of the estimated net proceeds to repay the $6.2 million note plus
accrued interest of $0.5 million as of December 31, 1998 payable to Lotus, to
repurchase for $  million   shares of common stock issued to holders of Class P
common stock in satisfaction of their preference amount, to pay $1.0 million to
terminate certain management fee arrangements, all as if they occurred on
December 31, 1998. You should read the data set forth below in conjunction with
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" and the Consolidated Financial Statements and Notes thereto
appearing elsewhere in this prospectus.
 
<TABLE>
<CAPTION>
                                                                      DECEMBER 31, 1998
                                                            --------------------------------------
                                                                                        PRO FORMA
                                                                         PRO FORMA     AS ADJUSTED
                                                             ACTUAL     (UNAUDITED)    (UNAUDITED)
                                                            --------    -----------    -----------
<S>                                                         <C>         <C>            <C>
Current portion of capital lease obligations(1)...........  $    471      $    471      $    471
                                                            ========      ========      ========
Long-term debt and capital lease obligations(1)...........     6,465         6,465           233
                                                            --------      --------      --------
Stockholders' equity (deficit):
  Preferred stock, $0.01 par value; no shares authorized,
     issued or outstanding, actual; 1,000,000 shares
     authorized, no shares issued or outstanding, pro
     forma; 1,000,000 shares authorized, no shares issued
     or outstanding, pro forma as adjusted................        --            --            --
  Class P common stock, $0.01 par value; 500,000 shares
     authorized, 352,400 shares issued and outstanding,
     actual; no shares authorized, issued or outstanding,
     pro forma; no shares authorized, issued or
     outstanding, pro forma as adjusted...................     3,524            --            --
  Common stock, $0.01 par value; 6,500,000 shares
     authorized, 3,329,392 shares issued and 3,275,392
     shares outstanding, actual; 20,000,000 shares
     authorized,                shares issued and
                    shares outstanding, pro forma;
     20,000,000 shares authorized,                issued
     and                shares outstanding, pro forma as
     adjusted(2)..........................................        33
  Additional paid-in capital..............................       759
  Unearned compensation...................................       (39)          (39)          (39)
  Accumulated deficit.....................................   (10,444)      (10,444)      (11,444)
  Accumulated other comprehensive loss....................      (138)         (138)         (138)
  Common stock held in treasury...........................        (6)           (6)
                                                            --------      --------      --------
     Total stockholders' equity (deficit).................    (6,311)
                                                            --------      --------      --------
          Total capitalization............................  $    154      $             $
                                                            ========      ========      ========
</TABLE>
 
------------
(1) For information regarding OneSource's long-term debt and capital lease
    obligations, see Notes 4 and 13 to the Consolidated Financial Statements.
(2) The number of shares of common stock issued and outstanding, pro forma as
    adjusted, excludes as of December 31, 1998, 1,983,852 shares of common stock
    issuable upon the exercise of stock options and warrants outstanding at a
    weighted average exercise price of $2.57, and an aggregate of 252,760 shares
    reserved for future stock option grants and purchases under OneSource's
    equity compensation plans. For more information, see "Management--Equity
    Plans" and Notes 7 and 8 to the Consolidated Financial Statements.
 
                                       16
<PAGE>   18
 
                                    DILUTION
 
     The net tangible book value per share of our common stock immediately after
this offering will be substantially less than the initial public offering price
because the assumed initial public offering price is substantially higher than
the current net tangible book value per share. The pro forma net tangible book
value deficit of OneSource as of December 31, 1998 was $(6.3) million, or
$(      ) per share. Pro forma net tangible book value per share represents the
amount of total tangible assets less total liabilities, divided by the number of
shares of common stock outstanding after giving effect to the reclassification
of all shares of Class P common stock into common stock and the issuance of
                shares of common stock to the holders of Class P common stock in
satisfaction of their preference amount. After giving effect to the sale by
OneSource of the                 shares of common stock offered hereby (at an
assumed initial public offering price of $     per share) and the application of
the estimated net proceeds, the pro forma net tangible book value of OneSource
as of December 31, 1998, would have been $           million, or $     per
share. This represents an immediate increase in pro forma net tangible book
value of $     per share to existing stockholders and an immediate "dilution" of
$     per share to investors purchasing common stock in this offering. The
following table illustrates this per share dilution:
 
<TABLE>
<S>                                                           <C>       <C>
Assumed initial public offering price.......................            $
  Pro forma net tangible book value deficit per share as of
     December 31, 1998......................................  $
  Increase per share attributable to new investors..........
                                                              ------
Pro forma net tangible book value per share after this
  offering..................................................
                                                                        -----
Dilution per share to new investors.........................            $
                                                                        =====
</TABLE>
 
     The following table summarizes, as of December 31, 1998, the difference
between the number of shares of common stock purchased from OneSource, the total
consideration paid to OneSource, and the average price per share paid by
existing stockholders and by new investors (at an assumed initial public
offering price of $     per share before deduction of the estimated underwriting
discount and offering expenses payable by OneSource):
 
<TABLE>
<CAPTION>
                                        SHARES PURCHASED        TOTAL CONSIDERATION
                                      ---------------------    ----------------------    AVERAGE PRICE
                                        NUMBER      PERCENT      AMOUNT       PERCENT      PER SHARE
                                      ----------    -------    -----------    -------    -------------
<S>                                   <C>           <C>        <C>            <C>        <C>
Existing stockholders...............                      %    $                    %       $
New investors.......................                                                        $
                                      ----------     -----     -----------     -----
     Total..........................                 100.0%    $               100.0%
                                      ==========     =====     ===========     =====
</TABLE>
 
     The foregoing tables (a) assume the repurchase of         of the shares of
common stock issued in the reclassification and (b) assume no exercise of the
options or the warrants outstanding as of December 31, 1998 to purchase an
additional         shares of common stock at a weighted average exercise price
of $     per share. To the extent these options or warrants are exercised, there
will be further dilution to new shareholders in the net tangible book value of
their shares. For more information, see "Management--Equity Plans." In addition,
the second table does not reflect the sale of         shares by the selling
stockholders in this offering. Such sales will reduce the number of shares held
by existing shareholders as of December 31, 1998 to                 , or
approximately      % of the total shares of common stock to be outstanding after
this offering (     % if the over-allotment option is exercised in full), and
will increase the number of shares to be purchased by the new shareholders to
                or      % (     % if the over-allotment option is exercised in
full) of the total shares of common stock to be outstanding after this offering.
For more information, see "Principal and Selling Stockholders."
 
                                       17
<PAGE>   19
 
                      SELECTED CONSOLIDATED FINANCIAL DATA
 
     The selected consolidated financial data set forth below should be read in
conjunction with OneSource's Consolidated Financial Statements and Notes thereto
and "Management's Discussion and Analysis of Financial Condition and Results of
Operations," appearing elsewhere in this prospectus. The consolidated statement
of operations data for the years ended December 31, 1996, 1997 and 1998, and the
consolidated balance sheet data as of December 31, 1997 and 1998, have been
derived from, and are qualified by reference to, OneSource's audited
Consolidated Financial Statements appearing elsewhere in this prospectus. The
consolidated statement of operations data for the years ended December 31, 1994
and 1995, and the consolidated balance sheet data as of December 31, 1994, 1995
and 1996, have been derived from audited Consolidated Financial Statements of
OneSource that do not appear in this prospectus. The historical results are not
necessarily indicative of the operating results to be expected in the future.
 
<TABLE>
<CAPTION>
                                                              YEAR ENDED DECEMBER 31,
                                                ----------------------------------------------------
                                                  1994       1995       1996       1997       1998
                                                --------   --------   --------   --------   --------
                                                  (IN THOUSANDS, EXCEPT SHARE AND PER SHARE DATA)
<S>                                             <C>        <C>        <C>        <C>        <C>
STATEMENT OF OPERATIONS DATA:
Revenues:(1)
  Web-based product...........................  $     --   $     --   $     15   $  3,312   $ 16,058
  CD Rom product..............................    30,300     28,957     30,419     27,072     14,370
                                                --------   --------   --------   --------   --------
  Total revenues..............................    30,300     28,957     30,434     30,384     30,428
                                                --------   --------   --------   --------   --------
Cost of revenues:
  Web-based product...........................        --         --        295      2,401      7,863
  CD Rom product..............................    12,380     11,520     12,244     10,444      5,792
                                                --------   --------   --------   --------   --------
  Total cost of revenues......................    12,380     11,520     12,539     12,845     13,655
                                                --------   --------   --------   --------   --------
Gross profit..................................    17,920     17,437     17,895     17,539     16,773
                                                --------   --------   --------   --------   --------
Operating expenses:
  Selling and marketing.......................    11,231      8,705      8,572      9,167     11,577
  Platform and product development............     5,512      6,585      7,252      6,375      6,313
  General and administrative..................     6,516      5,163      3,664      3,401      3,847
                                                --------   --------   --------   --------   --------
  Total operating expenses....................    23,259     20,453     19,488     18,943     21,737
                                                --------   --------   --------   --------   --------
Loss from operations..........................    (5,339)    (3,016)    (1,593)    (1,404)    (4,964)
Interest income (expense), net................      (515)      (633)      (733)      (930)      (595)
Gain on sale of product line..................        --         --         --        501     12,797
                                                --------   --------   --------   --------   --------
Income (loss) before income taxes and
  extaordinary gain...........................    (5,854)    (3,649)    (2,326)    (1,833)     7,238
Provision (benefit) for income taxes..........      (473)        --         --         --        250
Extraordinary gain on early extinguishment of
  debt........................................        --         --        393         --         --
                                                --------   --------   --------   --------   --------
Net income (loss).............................    (5,381)    (3,649)    (1,933)    (1,833)     6,988
Less: income (loss) attributable to Class P
  common stock................................      (122)       104        335        414      1,367
                                                --------   --------   --------   --------   --------
Income (loss) attributable to common stock....  $ (5,259)  $ (3,753)  $ (2,268)  $ (2,247)  $  5,621
                                                ========   ========   ========   ========   ========
Earnings (loss) per share:(2)
  Class P common stock:
    Basic and diluted earnings (loss) per
share.........................................  $  (0.34)  $   0.29   $   0.95   $   1.17   $   3.88
    Weighted average Class P common shares
       outstanding............................   355,900    355,400    353,300    352,800    352,600
</TABLE>
 
                                       18
<PAGE>   20
 
<TABLE>
<CAPTION>
                                                              YEAR ENDED DECEMBER 31,
                                                ----------------------------------------------------
                                                  1994       1995       1996       1997       1998
                                                --------   --------   --------   --------   --------
<S>                                             <C>        <C>        <C>        <C>        <C>
  Common stock:
    Basic earnings (loss) per share...........  $  (1.64)  $  (1.17)  $  (0.71)  $  (0.70)  $   1.72
    Diluted earnings (loss) per share.........  $  (1.64)  $  (1.17)  $  (0.71)  $  (0.70)  $   1.20
    Weighted average common shares
      outstanding:
       Basic..................................  3,206,431  3,205,223  3,187,695  3,216,385  3,263,309
       Diluted................................  3,206,431  3,205,223  3,187,695  3,216,385  4,699,337
  Unaudited pro forma earnings per share:(3)
    Basic.....................................                                              $
    Diluted...................................                                              $
    Weighted average common shares outstanding
       Basic..................................
       Diluted................................
</TABLE>
 
<TABLE>
<CAPTION>
                                                                    DECEMBER 31,
                                                ----------------------------------------------------
                                                  1994       1995       1996       1997       1998
                                                --------   --------   --------   --------   --------
                                                   (IN THOUSANDS, EXCEPT NUMBER OF CUSTOMER DATA)
<S>                                             <C>        <C>        <C>        <C>        <C>
BALANCE SHEET DATA:
Cash and cash equivalents.....................  $  1,378   $    966   $    535   $    341   $  8,665
Working capital (deficit).....................    (7,431)    (7,499)    (8,803)    (9,792)    (2,118)
Total assets..................................    19,396     16,567     16,934     16,644     27,646
Total debt (including capital lease
  obligations)................................     4,755      6,223      6,661      8,171      6,936
Deferred revenues.............................    13,818     14,160     15,419     15,748     18,022
Total stockholders' deficit...................    (6,116)    (9,757)   (11,827)   (13,613)    (6,311)
 
OTHER DATA FOR WEB-BASED PRODUCTS (UNAUDITED):
Annualized contract value(4)..................  $     --   $     --   $    412   $  8,973   $ 25,920
Number of customers...........................        --         --         11        233        445
Average annualized contract value per
  customer....................................  $     --   $     --   $   37.4   $   38.5   $   58.2
</TABLE>
 
------------
(1) In 1997 and 1998, OneSource divested certain CD Rom product lines. Revenues
    attributable to these divested product lines, which are included in the
    statement of operations data through the divestiture date, were $5,713,000,
    $6,002,000, $6,415,000, $6,630,000 and $2,612,000 in the years ended
    December 31, 1994, 1995, 1996, 1997 and 1998, respectively.
 
(2) You should read Notes 2 and 5 to the Consolidated Financial Statements for
    further description of the calculation of these items.
 
(3) Unaudited pro forma basic and diluted earnings per share of common stock for
    the year ended December 31, 1998 have been calculated based on net income
    attributable to all classes of common stock and assuming the
    reclassification of OneSource's Class P common stock prior to the completion
    of this offering as if it had occurred at January 1, 1998. In the
    reclassification, each share of Class P common stock will be reclassified
    into one share of common stock plus an additional number of shares of common
    stock (determined by dividing the preference amount for such share by the
    assumed initial public offering price of $        per share). As described
    in "Use of Proceeds", OneSource intends to use a portion of its net proceeds
    to repay a $6.2 million note due to Lotus Development Corporation and to pay
    $1.0 million to terminate certain management fee arrangements. Accordingly,
    had the note repayment and the management fee termination occurred at
    January 1, 1998, unaudited supplemental pro forma basic and diluted earnings
    per share for the year ended December 31, 1998 would be $        and
    $        , respectively. Such amounts reflect the elimination of annual
    interest expense on the note of $0.5 million and the elimination of annual
    management fees of $0.2 million, and the issuance of             shares of
    common stock at the assumed initial public offering price of $        per
    share necessary to fund the note repayment and management fee termination.
 
(4) Annualized contract value represents the invoiced fees for one month for all
    customer contracts for Web-based products in effect at the measurement date,
    multiplied by 12, without regard to the actual remaining duration of such
    contracts. At December 31, 1996, 1997 and 1998, annualized contract value
    was calculated by multiplying the total amount of fees invoiced for one
    month and included in deferred revenues for all customer contracts for
    Web-based products at December 31, 1996, 1997 and 1998 of $34,300, $747,750
    and $2,160,000, respectively, by 12. For more information regarding
    annualized contract value, see "Management's Discussion and Analysis of
    Financial Condition and Results of Operations."
 
                                       19
<PAGE>   21
 
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
OVERVIEW
 
     OneSource provides Web-based business and financial information to
professionals who need quick access to reliable corporate, industry and market
intelligence. OneSource was formed as a division of Lotus in 1987 and became an
independent company when it was purchased in a management buy-out in 1993. Until
December 1996, our business was to provide business information to the financial
community using CD Rom technology as the primary method of distribution. The
introduction of Business Browser in December 1996 marked a fundamental shift in
our business as we began a transition away from our legacy CD Rom business and
toward Web-based products.
 
     Revenues from Web-based products accounted for $16.1 million, or 53% of
total revenues, for the year ended December 31, 1998 up from $3.3 million, or
11% of total revenues, for the year ended December 31, 1997. In the same period,
CD Rom product revenues decreased to $14.4 million, or 47% of total revenues for
the year ended December 31, 1998 from $27.1 million, or 89% of total revenues,
for the year ended December 31, 1997. As of December 31, 1998, 445 organizations
subscribed to our Business Browser product line, and the annualized contract
value for these organizations was $25.9 million.
 
     During this transition period, we utilized the cash flow from our CD Rom
business to fund a portion of the significant expenses incurred to build our
Web-based business. These expenses included (a) platform and product development
expenses to develop and enhance our Web-based products, (b) selling and
marketing expenses to hire and train a Web-based sales force and to retrain a
portion of our CD Rom-based sales force and (c) general and administrative
expenses to build the necessary infrastructure to support our growing Web-based
business. The gross margins on our Web-based business have also been adversely
impacted by certain royalty expenses and other costs of revenues which were
disproportionately high compared to Web-based revenues which were growing from
low initial levels. We believe that our operating margins will improve as we
more effectively leverage our Web-based royalty and infrastructure expenses and
eliminate costs incurred to support our legacy CD Rom products.
 
     In May 1998, we sold our CD-Insurance division to allow us to focus more
completely on our new Web-based product line. We recognized a gain of $12.8
million on this sale during 1998. In addition, in connection with the
disposition, we licensed certain of our CD Rom technology to the acquiror in
exchange for $4.0 million of license fees. These license fees will be paid in
eight equal quarterly installments beginning January 1, 1999 and running through
December 31, 2000 and recognized ratably.
 
     One measure of the performance of our business is "annualized contract
value," a term we use as an indicator of business volume and growth, both in
terms of new customers and upgrades and expansions at existing customers. It is
not an absolute indicator and we cannot guarantee that any annualized contract
value will be ultimately realized as revenues. Annualized contract value
represents the total annualized revenue under all customer contracts for
Web-based products in effect at the measurement date, without regard for the
actual remaining duration of such contracts. We have increased annualized
contract value attributable to Web-based products 189% to $25.9 million as of
December 31, 1998 from $9.0 million as of December 31, 1997. The
 
                                       20
<PAGE>   22
 
number of on-line customers has increased 91%, to 445 at December 31, 1998 from
233 at December 31, 1997. At the same time, the average annualized contract
value of all Web-based product customers has increased 51%, to $58,248 per
customer at December 31, 1998 from $38,512 per customer at December 31, 1997.
The average annualized contract value for the customers that were under contract
at both December 31, 1997 and 1998 grew to $76,143 per customer at December 31,
1998 from $38,512 per customer at December 31, 1997. This growth was
attributable to an increase in the number of user seats purchased by customers
and the addition of new products.
 
     The renewal rate of the Business Browser product line for 1998 was 90%
calculated on a dollar basis. The renewal rate is measured by comparing a
customer's annualized contract value at December 31, 1998 to its annualized
contract value at December 31, 1997. The set of customers measured are those who
had subscriptions in effect at December 31, 1997.
 
     Our revenues (for both CD Rom and Web-based products) consist of monthly
subscription fees from customer contracts. Customer contracts span varying
periods of time but are generally for one year, are renewable for like periods,
and are payable in advance. Subscription fees generally are quoted to clients on
an annual basis but are earned as revenues on a monthly basis over the
subscription period. Invoices are recorded as accounts receivable until paid and
as deferred revenues until earned. Deferred revenues attributable to Web-based
products increased 231% to $15.9 million as of December 31, 1998 from $4.8
million as of December 31, 1997.
 
     Cost of revenues consists primarily of royalties to information providers
and, to a lesser extent, employee salaries and related expenses (including
benefits and facilities allocation), depreciation associated with computers for
data processing and on-line requirements and Web hosting expenses. We enter into
contracts with our information providers which are generally for a term of at
least one year and are automatically renewable if not canceled with advance
notice. These contracts may be terminated under certain circumstances. For more
information, see "Risk Factors--We depend entirely on our information providers
for content." Under these arrangements, royalties are generally paid on a
quarterly basis to information providers. Royalties generally are calculated
either as a flat percentage of our revenues or as a per-user fee that declines
as the number of authorized users of the product increases. In limited cases, we
pay a fixed fee per period.
 
     Selling and marketing expense consists primarily of employee salaries and
sales commissions paid to our sales force, customer support organization and
marketing personnel, as well as related expenses (including benefits and
facilities allocation), direct marketing promotional materials, trade show
exhibitions and advertising. Sales commissions are paid when customers are
invoiced and are recorded as deferred subscription costs, which are amortized
ratably over the term of the contract, typically 12 months, as the associated
revenues are recognized. All other selling and marketing costs are expensed as
incurred.
 
     Platform and product development expense consists primarily of employee
salaries and related expenses (including benefits and facilities allocation) as
well as outside contractor expenses, relating to the development of our
"platform" of core software supporting our products and the development of new
products based upon that platform. Platform and product development expense
includes expenses relating to the editorial staff that implements our KeyID
technology to integrate disparate information sources into our Web-based
products.
 
                                       21
<PAGE>   23
 
     General and administrative expense consists primarily of employee salaries
and related expenses (including benefits and facilities allocation) associated
with OneSource's management, finance, human resources, management information
systems and administrative groups. In addition, we will incur non-recurring
charges of (a) approximately $0.2 million in moving and related costs in June
1999 due to the relocation of our headquarters from Cambridge to Concord,
Massachusetts and (b) approximately $0.2 million of financial advisory fees. The
quarterly management fees of $25,000 paid to each of William Blair Venture
Partners and an affiliate of Information Partners Capital will cease in exchange
for the payment of a $0.5 million termination fee to each of these parties upon
completion of this offering. For more information, see "Certain Transactions."
 
RESULTS OF OPERATIONS
 
     The following table sets forth, for the periods indicated, the percentage
of total revenues represented by each line item in OneSource's consolidated
statement of operations. We can give no assurance that the indicated trends in
revenues or operating results will continue in the future.
 
<TABLE>
<CAPTION>
                                                              YEAR ENDED DECEMBER 31,
                                                          -------------------------------
                                                          1996         1997         1998
                                                          -----        -----        -----
                                                          (PERCENTAGE OF TOTAL REVENUES)
<S>                                                       <C>          <C>          <C>
Revenues:
  Web-based product.....................................    --%          11%          53%
  CD Rom product........................................   100           89           47
                                                           ---          ---         ----
     Total revenues.....................................   100          100          100
                                                           ---          ---         ----
Cost of revenues:
  Web-based product.....................................     1            8           26
  CD Rom product........................................    40           34           19
                                                           ---          ---         ----
     Total cost of revenues.............................    41           42           45
                                                           ---          ---         ----
Gross profit............................................    59           58           55
Operating expenses:
  Selling and marketing.................................    28           30           38
  Platform and product development......................    24           21           21
  General and administrative............................    12           11           12
                                                           ---          ---         ----
Loss from operations....................................    (5)          (4)         (16)
Interest income (expense), net..........................    (2)          (3)          (2)
Gain on sale of product line............................    --            1           42
                                                           ---          ---         ----
Income (loss) before income taxes and extraordinary
  gain..................................................    (7)          (6)          24
Provision for income taxes..............................    --           --            1
Extraordinary gain on early extinguishment of debt......     1           --           --
                                                           ---          ---         ----
Net income (loss).......................................    (6)%         (6)%         23%
                                                           ===          ===         ====
</TABLE>
 
                                       22
<PAGE>   24
 
COMPARISON OF RESULTS FOR THE YEARS ENDED DECEMBER 31, 1998 AND 1997
 
     Revenues.  Total revenues remained at approximately the same level of $30.4
million for each of the years ended December 31, 1998 and 1997. Web-based
product revenues increased by 385% to $16.1 million for the year ended December
31, 1998 from $3.3 million for the year ended December 31, 1997. The increase
was attributable to new customers, an increase in the number of user seats
purchased by existing customers and the sale of new products to existing
customers. At the same time, CD Rom product revenues decreased by 47% to $14.4
million in 1998 from $27.1 million in 1997 as OneSource continued its transition
away from its legacy CD Rom business. During this period, CD Rom product
revenues included revenues attributable to our CD-Insurance division which was
sold in May 1998. Revenues from this product line were $2.6 million for the year
ended December 31, 1998 compared to $6.6 million for the year ended December 31,
1997.
 
     Cost of Revenues.  Total cost of revenues increased 6% to $13.7 million for
the year ended December 31, 1998 from $12.8 million for the year ended December
31, 1997. As a percentage of total revenues, total cost of revenues increased to
45% in 1998 from 42% in 1997. The increase in total cost of revenues was
principally due to increased royalty expense for our Web-based products. It was
offset partially by a decrease in our costs of revenues relating to the CD Rom
product line.
 
     Cost of Web-based product revenues increased 227% to $7.9 million for the
year ended December 31, 1998 from $2.4 million for the year ended December 31,
1997. As a percentage of Web-based product revenues, cost of Web-based product
revenues decreased to 49% in 1998 from 72% in 1997, due to an increase in our
customer base. Royalty expense increased as a result of growth in Business
Browser product line revenues and number of user seats sold.
 
     Cost of CD Rom product revenues decreased 45% to $5.8 million for the year
ended December 31, 1998 from $10.4 million for the year ended December 31, 1997.
This decrease was due to decreased revenues reflecting our shift away from the
CD Rom product line. As a percentage of CD Rom product revenues, cost of CD Rom
product revenues increased to 40% in 1998 from 39% in 1997.
 
     Selling and Marketing Expense.  Selling and marketing expense increased 26%
to $11.6 million for the year ended December 31, 1998 from $9.2 million for the
year ended December 31, 1997 principally due to increased expenses incurred to
hire new sales personnel and to train new and existing personnel in connection
with our transition to our new Business Browser product line. Selling and
marketing expense increased as a percentage of total revenues to 38% in 1998
from 30% in 1997.
 
     Platform and Product Development Expense.  Platform and product development
expense decreased 1% to $6.3 million for the year ended December 31, 1998 from
$6.4 million for the year ended December 31, 1997, although as a percentage of
total revenues it remained constant at 21%. The decrease was due principally to
the decrease in salary expense resulting from the elimination of CD-Insurance
product development staff in May 1998 upon the sale of that division and the
elimination of several CD Rom product management positions. This decrease in
salary expense was offset by increased headcount in the Global Strategic Web
Applications Team to meet new product demands.
 
                                       23
<PAGE>   25
 
     General and Administrative Expense.  General and administrative expense
increased 13% to $3.8 million for the year ended December 31, 1998 from $3.4
million for the year ended December 31, 1997 principally due to increased
headcount in management information systems and human resources for
infrastructure required to accommodate the growth in our business. General and
administrative expense increased as a percentage of total revenues to 12% in
1998 from 11% in 1997.
 
     Interest Expense, Net.  Interest expense, net of interest income, decreased
36% to $0.6 million for the year ended December 31, 1998 from $0.9 million for
the year ended December 31, 1997 due to an increase in interest income related
to invested cash balances from the sale of the CD-Insurance product line in May
1998.
 
     Gain on Sale of Product Line.  As a result of the sale of the CD-Insurance
division, we recorded a gain of $12.8 million. This gain reflects cash proceeds
received of $11.0 million together with recognition of deferred revenues of $3.1
million and $0.6 million of deferred subscription costs due to the transfer of
related service obligations, net of transaction related expenses.
 
     Income Taxes.  The income tax provision for the year ended December 31,
1998 was $0.3 million and is directly related to the gain on the sale of the
CD-Insurance division. Although the gain on the sale created significant taxable
income for 1998, such gain was largely offset by utilizing our net operating
loss carryforwards.
 
COMPARISON OF RESULTS FOR THE YEARS ENDED DECEMBER 31, 1997 AND 1996
 
     Revenues.  Revenues remained at approximately the same level of $30.4
million for each of the years ended December 31, 1997 and 1996. Web-based
product revenues increased to $3.3 million for the year ended December 31, 1997
from $15,000 for the year ended December 31, 1996 due to the addition of new
customers. At the same time, CD Rom product revenues decreased by 11% to $27.1
million in 1997 from $30.4 million in 1996 as we began our transition to
Web-based products.
 
     Cost of Revenues.  Total cost of revenues increased 2% to $12.8 million for
the year ended December 31, 1997 from $12.5 million for the year ended December
31, 1996. As a percentage of total revenues, total cost of revenues increased
marginally to 42% in 1997 from 41% in 1996. This increase in total cost of
revenues was due principally to increased royalty expense for our Web-based
products. It was partially offset by a decrease in our costs of revenues
relating to the CD Rom product line.
 
     Cost of Web-based product revenues increased to $2.4 million for the year
ended December 31, 1997 from $0.3 million for the year ended December 31, 1996
due to a substantial increase in Web-based customers and related royalty
expenses. Cost of CD Rom product revenues decreased 15% to $10.4 million for the
year ended December 31, 1997 from $12.2 million for the year ended December 31,
1996. This decrease reflected our shift away from the CD Rom product line. As a
percentage of CD Rom product revenues, cost of CD Rom product revenues decreased
to 39% in 1997 from 40% in 1996.
 
     Selling and Marketing Expense.  Selling and marketing expense increased 7%
to $9.2 million for the year ended December 31, 1997 from $8.6 million for the
year ended December 31, 1996 principally due to increased headcount and related
expenses. Total selling
 
                                       24
<PAGE>   26
 
and marketing expense increased as a percentage of total revenues to 30% in 1997
from 28% in 1996.
 
     Platform and Product Development Expense.  Platform and product development
expense decreased 12% to $6.4 million for the year ended December 31, 1997 from
$7.3 million for the year ended December 31, 1996 principally due to the
decrease in headcount and related expenses, as well as lower contractor expense.
The reduction in headcount was exclusively in the platform development
organization as we ceased all development efforts related to the CD Rom platform
in 1997 and shifted all resources to Web-based platform and product development.
Platform and product development expense decreased as a percentage of total
revenues to 21% in 1997 from 24% in 1996.
 
     General and Administrative Expense.  General and administrative expense
decreased 7% to $3.4 million for the year ended December 31, 1997 from $3.7
million for the year ended December 31, 1996 principally due to the decrease in
amortization expense of intangibles. The amortization of $9.9 million of
intangibles, originally recorded in 1993 at the time of the management buy-out
of OneSource from Lotus, ended in 1997 with expense of $25,000 compared to $0.7
million in 1996. Increased salary and related expense, resulting from increased
headcount for infrastructure required to meet demands in management information
systems, contracting and UK finance management, partially offset the decrease in
amortization. General and administrative expense decreased as a percentage of
total revenues to 11% in 1997 from 12% in 1996.
 
     Interest Expense, Net.  Interest expense, net of interest income, increased
27% to $0.9 million for the year ended December 31, 1997 from $0.7 million for
the year ended December 31, 1996 due to increased borrowings for working capital
requirements in 1997.
 
     Gain on Sale of Product Line.  In June 1997, we sold our CD-Banking product
line for $0.7 million. As a result of the sale, we recorded a gain of $0.5
million which is net of transaction related expenses.
 
                                       25
<PAGE>   27
 
QUARTERLY RESULTS OF OPERATIONS AND OTHER DATA
 
     The following tables set forth a summary of OneSource's unaudited quarterly
operating results for each of the eight quarters in the two-year period ended
December 31, 1998. This information has been derived from unaudited interim
consolidated financial statements that, in the opinion of management, have been
prepared on a basis consistent with the Consolidated Financial Statements
appearing elsewhere in this prospectus and include all adjustments, consisting
of only normal recurring adjustments, necessary for a fair statement of such
information when read in conjunction with OneSource's Consolidated Financial
Statements and Notes thereto. Our operating results and other data for any
quarter are not necessarily indicative of results for any future period.
 
<TABLE>
<CAPTION>
                                                                          QUARTER ENDED
                                     ---------------------------------------------------------------------------------------
                                                        1997                                         1998
                                     ------------------------------------------   ------------------------------------------
                                     MAR. 31,   JUNE 30,   SEPT. 30,   DEC. 31,   MAR. 31,   JUNE 30,   SEPT. 30,   DEC. 31,
                                     --------   --------   ---------   --------   --------   --------   ---------   --------
                                                                         (IN THOUSANDS)
<S>                                  <C>        <C>        <C>         <C>        <C>        <C>        <C>         <C>
STATEMENT OF OPERATIONS DATA (UNAUDITED):
Revenues:
  Web-based product................   $  172     $  369     $  979      $1,792    $ 2,628    $ 3,419     $ 4,479    $ 5,532
  CD Rom product...................    7,348      7,383      6,309       6,032      5,322      4,273       2,725      2,050
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total revenues.....................    7,520      7,752      7,288       7,824      7,950      7,692       7,204      7,582
                                      ------     ------     ------      ------    -------    -------     -------    -------
Cost of revenues:
  Web-based product................      340        451        718         892      1,287      1,872       2,070      2,634
  CD Rom product...................    2,769      2,747      2,523       2,405      1,979      1,643       1,159      1,011
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total cost of revenues.............    3,109      3,198      3,241       3,297      3,266      3,515       3,229      3,645
                                      ------     ------     ------      ------    -------    -------     -------    -------
Gross profit.......................    4,411      4,554      4,047       4,527      4,684      4,177       3,975      3,937
                                      ------     ------     ------      ------    -------    -------     -------    -------
Operating expenses:
  Selling and marketing............    2,168      2,195      2,346       2,458      2,797      2,904       2,861      3,015
  Platform and product
    development....................    1,544      1,745      1,608       1,478      1,561      1,528       1,638      1,586
  General and administrative.......      929        749        686       1,037        957      1,051         897        942
                                      ------     ------     ------      ------    -------    -------     -------    -------
    Total operating expenses.......    4,641      4,689      4,640       4,973      5,315      5,483       5,396      5,543
                                      ------     ------     ------      ------    -------    -------     -------    -------
Loss from operations...............   $ (230)    $ (135)    $ (593)     $ (446)   $  (631)   $(1,306)    $(1,421)   $(1,606)
                                      ======     ======     ======      ======    =======    =======     =======    =======

                                                                 (PERCENTAGE OF TOTAL REVENUES)
Revenues:
  Web-based product................        2%         5%        13%         23%        33%        44%         62%        73%
  CD Rom product...................       98         95         87          77         67         56          38         27
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total revenues.....................      100        100        100         100        100        100         100        100
                                      ------     ------     ------      ------    -------    -------     -------    -------
Cost of revenues:
  Web-based product................        4          6         10          11         16         24          29         35
  CD Rom product...................       37         35         35          31         25         22          16         13
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total cost of revenues.............       41         41         45          42         41         46          45         48
                                      ------     ------     ------      ------    -------    -------     -------    -------
Gross profit.......................       59         59         55          58         59         54          55         52
                                      ------     ------     ------      ------    -------    -------     -------    -------
Operating expenses:
  Selling and marketing............       29         28         32          32         35         38          40         40
  Platform and product
    development....................       21         23         22          19         20         20          23         21
  General and administrative.......       12         10          9          13         12         13          12         12
                                      ------     ------     ------      ------    -------    -------     -------    -------
    Total operating expenses.......       62         61         63          64         67         71          75         73
                                      ------     ------     ------      ------    -------    -------     -------    -------
Loss from operations...............       (3)%       (2)%       (8)%        (6)%       (8)%      (17)%       (20)%      (21)%
                                      ======     ======     ======      ======    =======    =======     =======    =======
 
OTHER DATA FOR WEB-BASED PRODUCTS
  (AS OF THE QUARTER END)
  (UNAUDITED):                                           (IN THOUSANDS, EXCEPT NUMBER OF CUSTOMERS DATA)
Annualized contract value..........   $  981     $2,430     $4,815      $8,973    $11,854    $14,619     $19,754    $25,920
Number of customers................       37         92        149         233        279        322         386        445
Average annualized contract value
  per customer.....................   $ 26.5     $ 26.4     $ 32.3      $ 38.5    $  42.5    $  45.4     $  51.2    $  58.2
</TABLE>
 
                                       26
<PAGE>   28
 
     Annualized contract value represents the invoiced fees for one month for
all customer contracts for Web-based products in effect at the measurement date,
multiplied by 12, without regard to the actual duration of such contracts. At
March 31, June 30, September 30 and December 31, 1997 and March 31, June 30,
September 30 and December 31, 1998, annualized contract value was calculated by
multiplying the total amount of fees invoiced for one month and included in
deferred revenues for all customer contracts for Web-based products at March 31,
June 30, September 30 and December 31, 1997 and March 31, June 30, September 30
and December 31, 1998 of $81,750, $202,500, $401,250 and $747,750 and $987,850,
$1,218,250, $1,646,200 and $2,160,000, respectively, by 12.
 
     Our quarterly revenues, gross profits and results of operations have
fluctuated significantly in the past and we expect them to continue to fluctuate
significantly in the future. In addition, we believe that an important measure
of our business is the annualized contract value at the end of each period,
which also may fluctuate. Causes of such fluctuations have included and may
include, among other factors:
 
        - changes in demand for our products
 
        - the dollar value and timing of both new and renewal subscriptions
 
        - competition (particularly price competition)
 
        - changes in operating expenses
 
        - technical difficulties or system downtime affecting our products on
          the Web generally
 
        - economic conditions specific to the Web, as well as general economic
          conditions
 
        - consolidation of our customers
 
In addition, a substantial portion of our expenses, including certain product
development and selling and marketing expenses, must be incurred in advance of
revenue generation. If our projected revenue does not meet our expectations,
then we may have an operating loss in a particular quarter.
 
     Annualized contract value depends upon the timely renewal, upgrade and sale
to new customers of subscription agreements within a quarter and can be
difficult to forecast accurately. In addition, we have experienced some
quarterly seasonality in contract bookings with a significant amount of activity
occurring in the fourth quarter of a given year. Accordingly, these timing
variations can create shortfalls in revenues in relation to our expectations and
have an adverse effect on our operating results.
 
LIQUIDITY AND CAPITAL RESOURCES
 
     Since acquiring our business from Lotus in 1993, we have funded our
operations through a combination of seller financing, proceeds received from the
sale of Class P common stock and common stock in connection with the purchase of
the business from Lotus, bank debt, proceeds received from the sale of
non-strategic lines of business, capitalized equipment leases and cash flows
from operations.
 
     Our cash and cash equivalents totaled $8.7 million at December 31, 1998, as
compared to $0.3 million at December 31, 1997, an increase of $8.3 million. Net
cash of $1.2 million was provided by operations for the year ended December 31,
1998, primarily resulting from growth in contracts invoiced for the period. Net
cash provided by investing activities for 1998 was $9.0
 
                                       27
<PAGE>   29
 
million, primarily reflecting net cash proceeds from the sale of the
CD-Insurance division, offset partially by expenditures of $1.3 million for
property and equipment. Net cash used in financing activities for the year ended
December 31, 1998 was $2.0 million reflecting primarily repayments on our line
of credit, term loan and capital lease obligations.
 
     We do not currently have a line of credit but intend to enter into a
revolving line of credit for letters of credit and general working capital.
 
     We have a note outstanding to Lotus and the principal amount outstanding at
December 31, 1998 was $6.2 million. This note plus accrued interest is due
September 8, 2000 and a repayment of a portion of the note would be required
upon completion of this offering. We intend to repay the note upon the
completion of this offering. Upon repayment of the note, the company will
recognize a one-time expense of $        relating to the unamortized portion of
the original issue discount.
 
     We currently anticipate capital expenditures of approximately $2.8 million
for 1999, including approximately $0.9 million in connection with the relocation
of our corporate headquarters, which is scheduled to occur in June 1999.
 
     We expect to investigate the possibility of investing in or acquiring
complementary businesses, products or technologies, although we have not entered
into any commitments or negotiations with respect to any such transactions.
 
     We believe that our net proceeds from this offering, together with our
current cash and cash equivalents and funds anticipated to be generated from
operations, will be sufficient to satisfy working capital and capital
expenditure requirements for at least the next twelve months.
 
YEAR 2000 READINESS DISCLOSURE STATEMENT
 
     We have established a Year 2000 compliance program and we anticipate that
our products and internal systems should operate correctly at the turn of the
century. We have been performing Year 2000 tests for the past three years.
Initial Year 2000 work was organized in late 1996 to certify readiness of the
proprietary client software associated with our CD Rom product line. A more
formal organizational effort involving senior management, product managers,
developers and quality assurance personnel was established in early 1998.
 
     Compliance Program.  The scope of OneSource's compliance program focuses on
four key areas: products, third-party information providers, third-party
software applications and internal systems. Our compliance program involves a
three-step process to evaluate each of the key areas, which includes (a)
inventory review, (b) assessment/testing and (c) resolution and contingency
planning.
 
     Products.  We have assessed existing products to review OneSource's overall
compliance status. We have decided not to test those products that will be
discontinued prior to December 31, 1999. This includes, for example, all
products associated with our CD Rom product line with the exception of the "UK
Companies" product, which we expect to produce beyond 1999. We have established
clear migration paths for those customers who have products installed that will
be discontinued. As of February 1999, we had completed almost all work
associated with creating internal company awareness of Year 2000 issues,
organizing and executing high-level plans to address the concern, and
inventorying existing systems, data, and software dependency for Year 2000
exposure. We estimate that as of February 1999 we had
 
                                       28
<PAGE>   30
 
completed about two-thirds of the process of analyzing the impact of Year 2000
issues company-wide and developing detailed plans for resolving problem
situations. We are in the midst of implementing those plans. Resolution of
outstanding Year 2000 issues for non-Information Services applications are being
incorporated with plans to move our corporate offices in June 1999. Projects
that involve IS-related issues (particularly those processes that prepare and
deliver data in our products) are expected to be completed in April 1999, with
follow-up testing, if required, extending through July 1999. In terms of
verifying and planning for Year 2000 compliance for our products, we use the
British Standards Institute's definition of Year 2000 compliance as stated in
DISC PD2000-1:1998: A Definition of Year 2000 Conformity Requirements. According
to this definition, Year 2000 conformity means that neither performance nor
functionality is affected by dates prior to, during and after the year 2000, and
according to the following rules:
 
        - No value for current date will cause any interruption in operation
 
        - Date-based functionality must behave consistently for dates prior to,
          during and after the year 2000
 
        - In all interfaces and data storage, the century in any date must be
          specified either explicitly or by unambiguous algorithms or
          inferencing rules
 
        - Year 2000 must be recognized as a leap year
 
     New products under development for this year and next have Year 2000
qualification as part of their standard test plans. Products that fail their
standard test plans are not released to customers.
 
     Third-Party Information Providers.  OneSource relies on content provided by
third-party information providers. Communication with our information providers
with respect to their Year 2000 compliance status was largely complete as of
February 1999. OneSource's goal is to have all information providers' compliance
responses complete by March 31, 1999. We are also trying to minimize our
dependence on third-party information providers' external date formats by
accommodating changes in date format within our existing production processes.
 
     Third-Party Application and System Software.  OneSource invests in
third-party software as components of the data storage and delivery requirements
of our products. We have identified an exhaustive list of such systems along
with research of the current status of their Year 2000 compliance efforts. We
completed this research in February 1999. Our goal is to have confirmation of
compliance or a specific plan to replace any non-compliant resource by March 31,
1999. Only a short list of these resources remains non-compliant as of February
1999. While OneSource is committed to taking every reasonable action to obtain
assurances from such business partners that their software is Year 2000
compliant, we cannot guarantee the performance of such business partners or
predict whether any of the assurances provided by them may be accurate or
realistic.
 
     Internal Systems.  OneSource has completed its inventory of its internal
systems and its assessment of such systems' compliance status is approximately
50% complete, with an anticipated completion date of March 31, 1999. The scope
of these systems ranges from accounting, payroll, communications, network
hardware and applications, Internet access, internal information systems and
data production systems. The majority of our internal systems and equipment are
currently Year 2000 compliant. Some existing Year 2000 issues (e.g.,
 
                                       29
<PAGE>   31
 
OneSource's phone switch and some components of the Corporate Local Area
Network) will be addressed as part of the relocation of our offices in June
1999.
 
     Costs.  To date we have not relied on outside consulting expertise for
assessing our products or testing for Year 2000 related issues. We are utilizing
internal personnel to identify Year 2000 readiness in our supported products,
network hardware/applications, internal business and information systems. A
large number of our personnel are necessarily involved in this work. We estimate
that the aggregation of all such efforts represents an equivalent of six
full-time employees (efforts at this level dating back approximately one year).
Not included in this estimate are those indirect costs associated with time
spent by management or staff discussing Year 2000 issues internally or with
third parties. Such discussions are handled by existing employees in the
ordinary course of business. We have not identified the need to hire additional
staff specifically to address third-party questions or concerns.
 
     Risks.  With regard to third-party information suppliers, OneSource is
addressing, through normal operating procedures any concerns that third-party
information providers may have delivery problems associated with Year 2000
issues. OneSource is identifying issues by internal quality assurance or
editorial reviewers. When identified, issues are being handled by contacting the
information provider who may correct the problem at the source or by developing
a workaround in the software. The risks associated with delivery problems
present more serious issues for us as our products could be deprived of certain
data content.
 
     While OneSource does not anticipate a failure in its ability to deliver
data, and has established contingency plans as discussed below, such a failure
may (a) have a material adverse effect upon our business, financial condition
and results of operations, (b) require us to incur unanticipated material
expenses to remedy any problem and (c) result in litigation due to our inability
to fulfill our contractual obligations. In such cases, we would likely suffer a
disruption in our revenue stream and operations could be materially impacted.
 
     Contingency Plans.  At this time, our contingency plans relating to the
above discussed Year 2000 issues include having additional support staff and
programmers on call for rapid response dealing with any disruption of our
business during a critical date transition (e.g., January 1, 2000, February 29,
2000). Our assessment of our products and internal systems for Year 2000
compliance will be an ongoing effort throughout the remainder of this year. The
information contained herein is the product of conclusions made from the
information and test results available to OneSource at this time.
 
RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS
 
     In March 1998, the Accounting Standards Executive Committee ("AcSEC")
issued Statement of Position ("SOP") 98-1, "Accounting for the Costs of Computer
Software Developed or Obtained for Internal Use." SOP 98-1 establishes the
accounting for costs of software products developed or purchased for internal
use, including when such costs should be capitalized. We do not expect SOP 98-1,
which is effective for OneSource beginning January 1, 1999, to have a material
effect on our financial condition or results of operations.
 
     In April 1998, the AcSEC issued SOP 98-5, "Reporting on the Costs of
Start-Up Activities." Start-up activities are defined broadly as those one-time
activities relating to opening a new facility, introducing a new product or
service, conducting business in a new territory,
 
                                       30
<PAGE>   32
 
conducting business with a new class of customer, commencing some new operation
or organizing a new entity. Under SOP 98-5, the cost of start-up activities
should be expensed as incurred. SOP 98-5 is effective for OneSource's calendar
year 1999 financial statements and we do not expect its adoption to have a
material effect on our financial condition or results of operations.
 
     In June 1998, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards ("SFAS") No. 133, "Accounting for Derivative
Instruments and Hedging Activities." The new standard establishes accounting and
reporting standards for derivative instruments, including certain derivative
instruments embedded in other contracts, and for hedging activities. SFAS No.
133 is effective for all fiscal quarters of fiscal years beginning after June
15, 1999. We do not expect SFAS No. 133 to have a material effect on our
financial condition or results of operations.
 
                                       31
<PAGE>   33
 
                                    BUSINESS
 
     This prospectus contains certain forward-looking statements that involve
substantial risks and uncertainties. Our actual results, performance or
achievements could differ materially from the results expressed in or implied by
these forward-looking statements. Factors that could cause or contribute to such
differences include those discussed in "Risk Factors."
 
OVERVIEW
 
     OneSource provides Web-based business and financial information to
professionals who need quick access to reliable corporate, industry and market
intelligence. Our Business Browser product line integrates comprehensive and
up-to-date business and financial information on over one million public and
private companies from more than 25 information providers drawing upon over
2,500 sources of content. These sources include both textual information, such
as news, trade press, SEC filings, executive biographies and analyst reports,
and numeric information, such as company financial results, stock quotes and
industry statistics. Our customers access this information over the Internet
using standard Web browsers at a fixed annual subscription price.
 
     Our products are designed to address information needs of leading
professional and financial services firms, technology companies and other large
organizations. Representative customers include American Express, Bain &
Company, BankAmerica, Boeing, British Telecom, Deloitte & Touche, Ernst & Young,
Harvard Business School, KPMG Peat Marwick, MCI/Worldcom, Merrill Lynch, Oracle
and SAP.
 
     At December 31, 1998, 445 organizations subscribed to our Web-based
Business Browser product line, up from 233 at December 31, 1997. On average, our
customers for Web-based products at December 31, 1998 had an annualized contract
value of $58,248 per customer, compared to $38,512 per customer at December 31,
1997. The annualized value of Business Browser customer contracts was $25.9
million at December 31, 1998, having grown from $9.0 million at the end of 1997.
Of this $25.9 million, $14.2 million was attributable to those customers that
were under contract at both December 31, 1997 and 1998. The renewal rate of the
Business Browser product line for 1998 was 90% calculated on a dollar basis.
 
INDUSTRY BACKGROUND
 
     According to an industry source, the market for all Web-based and on-line
business information services was $24.8 billion in 1997 and is projected to grow
to $39.8 billion in 2002, reflecting a compound annual growth rate of 9.9%.
According to this industry source, the primary market segment in which OneSource
participates--Web-based and on-line financial news, current awareness and
research services--was $5.4 billion in 1997 and is projected to grow to $9.8
billion in 2002, reflecting a compound annual growth rate of 12.6%.
 
     Recent industry growth has been driven by corporations and other
enterprises recognizing that productivity and competitiveness depend on
extensive knowledge of external information, including information about
industries, customers, competitors, prospects, business trends, breaking news
and market data. These organizations have already invested heavily in Internet
connectivity and networked computing infrastructures to manage internal
information and are seeking to leverage these infrastructures to access and
manage external information.
 
                                       32
<PAGE>   34
 
     The task of finding and using external information is often difficult and
cumbersome. Traditional, textual sources such as newspapers and directories
require hours to search. A centralized library can be costly to establish and
maintain and can be an inefficient and incomplete information source. While the
emergence of the Web has greatly increased access to information, finding
comprehensive, precise, up-to-date, relevant and reliable information on the Web
can still be time-consuming and difficult. While other on-line services can be
useful research tools in certain circumstances, most of these services currently
focus on specific areas of content, such as financial data or news. They do not
provide the full range of data required by professionals. In addition, most
on-line services charge a fee for each search performed.
 
     Traditional sources, the Web and existing on-line services do not
adequately meet the information needs of many professionals who want to compete
effectively in today's fast-paced, global, customer-focused marketplace. These
professionals and their organizations demand external information that is:
 
        - easily accessible in a user-friendly format
 
        - comprehensive and includes both textual and numeric information
 
        - derived from multiple, high quality sources
 
        - integrated at a single site
 
        - delivered on a platform that allows interpretation, manipulation and
          analysis
 
        - available throughout the enterprise at a fixed cost
 
        - delivered in a product easily implemented and supported on a corporate
          network
 
THE ONESOURCE SOLUTION
 
     OneSource's Business Browser product line is designed to be a comprehensive
and easy to use business and financial information resource for professionals
who need quick access to reliable corporate, industry and market intelligence.
 
     Business Browser products integrate over 2,500 sources of business
information from more than 25 category-leading business and financial
information providers. These sources include both textual information, such as
news, trade press, SEC filings, executive biographies and analyst reports, and
numeric information, such as company financial results, stock quotes and
industry statistics. OneSource uses its proprietary KeyID technology to sort,
prioritize, integrate and link information on over one million public and
private companies worldwide.
 
     Our Business Browser product line is accessed through a standard Web
browser that is already available and familiar to end-users. Because our
products are based on standard Web technology, our customers require minimal
installation and systems support and users have full access to the products at
any time from anywhere via the Internet.
 
     OneSource focuses on the functional uses of the business and financial
information it delivers. The Business Browser product line has been designed for
use not only by traditional users of business information, but also throughout
an organization, including sales, marketing, finance and management
professionals. We apply our knowledge of how business professionals use
information to transform raw, disparate data into meaningful, actionable
information. We focus on integrating and presenting information so that
interpretation, manipulation and analysis
 
                                       33
<PAGE>   35
 
can be performed more easily by the end user. Because the interface is built
around the inquiries of professionals, users require minimal training to become
productive quickly.
 
     OneSource's pricing strategy is designed to be particularly attractive to
large organizations. The Business Browser product line is available at a fixed
annual subscription price which declines on a per-user basis as the total number
of users increases for that customer. The fixed-price model encourages
professionals to use the products as needed without concern with additional
charges, and a declining marginal price per user encourages customers to
distribute our products widely throughout their organizations.
 
STRATEGY
 
     Our goal is to become a leading Web-based provider of business and
financial information to professionals worldwide. To accomplish that goal, we
have adopted the following strategies:
 
     --Focus on Information Needs of Professionals in Large Organizations.  We
believe that professional and financial services firms, technology companies and
other large organizations have the widely distributed Web access necessary to
take advantage of the Business Browser product line and are most likely to be
willing to purchase external information services to gain the competitive
advantages available through our products. While many alternative products are
focused on small organizations and individual consumers, our product and pricing
strategies and sales and marketing efforts have been designed to address the
needs of large enterprises.
 
     --Expand Customer Base.  At December 31, 1998, 445 organizations subscribed
to our Web-based Business Browser product line, up from 233 at December 31,
1997. One group of our direct sales force, our account executives, concentrates
primarily on selling the Business Browser product line to new customers. We
intend to continue to invest in training our sales force and in recruiting
technically qualified sales personnel to sell Business Browser products. In
addition, while the traditional users of on-line business information services
have been primarily financial analysts and professional service providers, we
have expanded our target customer base to include corporations which are
purchasing our products for use by their sales, marketing, finance and
management professionals. We also intend to explore selective third-party
distribution of our products primarily to expand geographic coverage. For
example, we recently entered into an agreement with Dun & Bradstreet under which
they will serve as a distributor of our European Business Browser product.
 
     --Leverage Existing Customer Base.  We will continue to seek to increase
sales to existing customers by expanding the number of authorized user seats at
each customer and by upgrading customers to new products, more extensive content
and increased functionality. Each customer is assigned an account manager who is
responsible for that customer's retention, monitoring that customer's needs and
assisting that customer with rollouts and upgrades. The average annualized
contract value at December 31, 1998 of Business Browser customers who were also
customers at December 31, 1997 was $76,143 per customer, compared to $38,512 per
customer at December 31, 1997, an increase of 98% during the course of the year.
 
     --Expand Content and Product Offerings.  Since introducing Business Browser
in December 1996, we have followed a strategy of enhancing the Business Browser
product line by adding content from new sources, increasing functionality and
designing products tailored to particular markets. For example, in January 1999
we introduced European Business Browser, which includes content focused on the
European market, and in December 1998 we introduced
 
                                       34
<PAGE>   36
 
AppLink, which permits customers to integrate content from Business Browser
products within the customer's own intranet applications, such as sales force
automation applications.
 
     --Strategic Alliances and Possible Acquisitions.  We will seek to expand
our distribution channels in part by seeking strategic alliances with partners,
such as vendors of sales automation software, who may use AppLink to integrate
content from the Business Browser products into their software offerings. In
addition, OneSource may seek additional content sources, distribution channels
or technology through selective acquisitions or strategic alliances, although we
are not currently in discussions regarding any potential acquisitions or
alliances.
 
PRODUCTS
 
  Business Browser Product Line
 
     The Business Browser product line includes:
 
     US BUSINESS BROWSER.  Released in December 1996, US Business Browser is
focused specifically on the US and Canada. It contains a subset of business and
financial information from the Global Business Browser product. It covers over
250,000 public and private companies in the US and Canada.
 
     UK BUSINESS BROWSER.  Released in September 1997, UK Business Browser is a
comprehensive source of information on over 350,000 public and private companies
in the UK.
 
     GLOBAL BUSINESS BROWSER.  Released in December 1997, Global Business
Browser is a single, integrated resource that provides information on over
350,000 public and private companies from around the world.
 
     EUROPEAN BUSINESS BROWSER.  Released in January 1999, European Business
Browser provides users with a comprehensive database on 300,000 public and
private companies across Europe, including 50,000 UK companies. An important
source of data for the European Business Browser is Dun & Bradstreet, a leading
business information source.
 
     Business Browser delivers information in an integrated format. This allows
customers to obtain different types of information from multiple sources in a
single report. Business Browser products organize data around business
applications and transform raw, disparate data into meaningful, actionable
information, delivered according to the characteristics users have defined and
in the custom formats, tables and reports that users require. Users who need to
perform detailed analysis can also easily transfer quantitative data into
spreadsheets or other desktop tools, such as contact management software.
 
     Specific applications available through the Business Browser product line
include:
 
        - "Company Profiler" delivers integrated reports on a company's history,
          products, competition, industry, executives, current news articles and
          financials. Both summary and detailed company reports are available,
          depending on the user's need. In addition, "Corporate Family Reports"
          allow users to quickly map relationships among subsidiaries and
          divisions of corporations.
 
        - "WatchList Update" automatically keeps track of new articles, news
          stories, financial filings and research reports on the companies the
          user monitors.
 
        - "Industry Profiler" delivers reports on market size, segmentation,
          financial norms, ratios and forecasts for a specified industry, as
          well as participants, industry news and
 
                                       35
<PAGE>   37
 
          analysis, and creates research reports with graphs and statistics that
          help track industry trends.
 
        - "Company Finder" screens companies by defining key search
          characteristics to deliver a targeted list by industry, geography,
          size, revenues, employment or other key characteristics.
 
        - "Topic Search" screens news stories, research reports, business
          descriptions and trade articles for information by topic.
 
        - "Executive Search" provides users with reports on business leaders by
          name, company, location, schools and affiliated organizations.
 
  Additional Software Applications
 
     Two additional software applications are available with Business Browser
products.
 
     BUSINESS BROWSER AP.  Business Browser AP, which became commercially
available in August 1997, is an advanced Web-based quantitative analysis tool
available as an option with all of the Business Browser products other than
European Business Browser. Business Browser AP lets users screen across a wide
range of public company financial statement items, ratios, growth rates and
other criteria. It also allows users to produce detailed quantitative reports of
their own design. Business Browser AP also makes EDGAR documents more user
friendly by removing confusing computer codes, formatting tables for easy
viewing and printing, and allowing users to export tables to a spreadsheet.
 
     BUSINESS BROWSER APPLINK.  Business Browser AppLink, which became
commercially available in December 1998, is a software toolkit that allows
customers to easily incorporate Business Browser content (e.g., company
profiles, news, business and trade articles, analyst reports, executive
biographies, industry intelligence and financial data) directly into corporate
intranet applications. Users have the ability to integrate in-depth, objective
external business information into their existing internal applications such as
prospect and customer databases, sales force automation tools, enterprise
reporting software and corporate Web applications. No special client software or
dedicated servers are necessary. AppLink-enabled applications are currently
under development at a number of client sites.
 
  Legacy CD Rom Products
 
     Prior to our introduction of Business Browser in 1996, we distributed
business information on CD Rom. Having made the strategic decision to transition
to a completely Web-based business, we began in 1998 to phase out our CD Rom
products. We expect that all but two of these products will be completely phased
out by the end of 1999, with the remaining two products being phased out shortly
thereafter.
 
PLATFORM AND PRODUCT DEVELOPMENT
 
     The product development function is currently carried out by 38 employees
in our Global Strategic Web Applications Team. This team includes product
managers who define functional software components, end user interfaces, report
formats and content requirements; product development engineers who take content
feeds from information partners and write database loader code; and the KeyID
team whose role, through both programming and editorial expertise,
 
                                       36
<PAGE>   38
 
is to ensure consistent integration and presentation of information from
multiple underlying sources of content.
 
     Our product development strategy is to deliver a broad range of information
on a software platform which allows end users to efficiently research their
business questions. Since the inception of the Business Browser product line, we
have consistently added sources of content and improved the software
functionality for users. In the future, we expect to continue to make these
types of improvements to our product line.
 
     The product development team uses our proprietary KeyID technology to
integrate and link public and private companies worldwide from multiple
databases, each with its own set of incompatible identifiers. Through a
combination of proprietary programmatic and editorial means, this technology
enables us to provide a single and unified presentation from multiple underlying
company databases. It also manages multiple SIC codes and industry mappings
assigned to companies by disparate databases and reclassifies the companies to
comparable categories. The system also keeps track of company name synonyms to
allow searching by commonly used alternative company names. The synonyms feature
allows the user to input one company name or term and to access all information
for that company although it may be categorized under different names or terms
depending on the database. In total, the KeyID database contains 1.1 million
companies, 1.7 million synonyms and 40,000 URLS.
 
                                       37
<PAGE>   39
 
INFORMATION PROVIDERS
 
     Each Business Browser product combines an array of carefully chosen
financial, company, industry, executive and news-related content obtained from
leading business and financial information providers identified by our Global
Strategic Web Applications Team. The following table lists the type of content
provided by our current information providers and which Business Browser
products include that content.
 
<TABLE>
<CAPTION>
                                                                    BUSINESS BROWSER PRODUCT
                                                                    -------------------------
      TYPE OF INFORMATION              INFORMATION PROVIDER         GLOBAL   US    UK    EURO
      -------------------              --------------------         ------   ---   ---   ----
<S>                              <C>                                <C>      <C>   <C>   <C>
Company Information............  CorpTech                             X       X
                                 Dun & Bradstreet                                         X
                                 Extel (Primark)                      X
                                 Graham & Whiteside Limited           X
                                 Hemmington Scott                                   X
                                 Hoover's Inc.                        X       X
                                 ICC                                                X
                                 InfoUSA                              X       X
                                 Market Guide                         X       X
                                 Reed Elsevier                        X       X
                                 Worldscope (Disclosure Inc.)         X
Industry Reports and Data......  McGraw-Hill                          X       X
                                 Integra                              X       X
                                 The Gale Group                       X       X
                                 Snapshots Intl                       X       X     X     X
News and Newsletters...........  Asia Pulse                           X       X     X     X
                                 Comtex News                          X       X     X     X
                                 Phillips Newsletters                 X       X     X     X
                                 Reuters News                         X       X     X     X
Business and Trade Press.......  Responsive Database Services         X       X     X     X
                                 Information Access Company           X       X     X     X
Executive Biographies..........  Marquis Who's Who                    X       X
                                 Standard & Poor's Register           X       X
Stock Quotes...................  Datastream                                         X
                                 Quote.com                            X       X
Investment Reports.............  Investext                            X       X     X
Published Statistical Tables...  Responsive Database Services         X       X
SEC Filings....................  EDGAR                                X       X
</TABLE>
 
     We enter into contracts with our information providers which are generally
for a term of at least one year, and which renew for the same period if not
canceled with advance notice. These contracts may be terminated under certain
circumstances. For more information, see "Risk Factors--We depend entirely on
our information providers for content." Under these arrangements, royalties are
generally paid on a quarterly basis to information providers. Royalties are
typically calculated either as a flat percentage of our revenues or as a
per-user fee that declines as the number of authorized users of the product
increases. In limited cases, we pay a fixed fee per period for unlimited use of
the information.
 
                                       38
<PAGE>   40
 
CUSTOMERS
 
     At December 31, 1998, 445 organizations had subscribed to our Web-based
Business Browser product line, up from 233 at December 31, 1997. On average, our
customers at December 31, 1998 had an annualized contract value of $58,248 per
customer, compared to $38,512 per customer at December 31, 1997. The annualized
contract value of customer contracts for Business Browser products was $25.9
million at December 31, 1998, having grown from $9.0 million at December 31,
1997. The following is a representative list of significant customers in each of
our primary industry sectors:
 
PROFESSIONAL SERVICES
Arthur Andersen
Arthur D. Little
Bain & Company
Cambridge Technology Partners
Deloitte & Touche
EDS
Ernst & Young
KPMG
Watson Wyatt
 
OTHER CORPORATIONS
Avery Dennison
Bayer
Boeing
Cargill
Coca Cola
General Electric
Johnson & Johnson
Pitney Bowes
Sears

FINANCIAL SERVICES
American Express
BankAmerica
Bank of Tokyo
Bear Stearns
Credit Lyonnais
First Union Bank
Merrill Lynch
Oppenheimer
Royal Bank of Canada
 
BUSINESS SCHOOLS
Dartmouth
Duke
Harvard
Stanford
University of Florida
University of Southern California
University of Texas
Yale

TECHNOLOGY
AT&T
British Telecom
Compaq
GTE
JD Edwards
Lockheed Martin
MCI/Worldcom
Nortel
Oracle
PeopleSoft
SAP
Sun Microsystems
 
     At December 31, 1998, approximately 60% of our annualized contract value
for Web-based products came from customers in the professional services and
financial services sectors, which have been the traditional customers for
business information products. The remaining 40% of our annualized contract
value at December 31, 1998 for Web-based products represented customers in
sectors that have not historically been heavy consumers of business information
products. At these customers, Business Browser products are used by
professionals throughout the organization, including sales, marketing, finance
and management personnel, as a result of the products' ease of use and
availability over the Web.
 
SALES AND MARKETING
 
     We market our products through a direct sales force and marketing staff,
which as of December 31, 1998 consisted of 67 full-time employees based at five
locations throughout the US and one location in the UK. The sales function
breaks down into two major parts:
 
        - the initial sale, which is conducted by account executives
 
        - customer retention and growth through the sale of additional seats and
          upgrades, which are primarily handled by account managers
 
                                       39
<PAGE>   41
 
     As of December 31, 1998, we had 20 account executives and 12 account
managers. Compensation for account executives and account managers is comprised
of base salary plus commission. The commission component typically constitutes
50% and 40% of the compensation of account executives and account managers,
respectively. We also employ a telemarketing group which assists in generating
leads for the account executives. As of December 31, 1998, there were ten
members of the telemarketing group.
 
     Business Browser products are sold on a subscription basis, generally for a
one-year period. Customers typically prepay for annual subscriptions. Typically,
contracts automatically renew for the same period prior to expiration unless
canceled by the client. The Business Browser product line is available at a
fixed annual subscription price which declines on a per-user basis as the total
number of users increases. The fixed-price model encourages business
professionals to use the products as needed without concern with additional
charges, and a declining marginal price per user encourages customers to
distribute the products widely throughout their organizations. List prices as of
January 1, 1999 ranged from $20,000 per year for a single user seat to $290,000
per year for 1,000 user seats.
 
CUSTOMER SUPPORT
 
     We provide both on-site and telephone support for clients. As of December
31, 1998, we had eight field support consultants who provide assistance before
and after sales are completed. For example, they assist in managing a product
trial for a prospective customer and expanding the availability of our products
to additional users through training and rollout initiatives within an
organization. They also provide technical consulting which may be requested,
such as the customization of Web pages for large clients or the building of
prototype applications using AppLink.
 
     As of December 31, 1998, we had six telephone-based customer support
representatives in the U.S. and one in the UK. These representatives operate the
telephone help desk which is open from 8:00 a.m. to 8:00 p.m. Monday through
Friday.
 
WEBSITE TECHNOLOGY AND OPERATIONS
 
     OneSource has designed its Website architecture to be open, flexible,
scaleable and reliable. The architecture is designed to accommodate an evolving
collection of third-party technologies that together provide the functionality
required by our products' applications. These technologies are adapted and
integrated with software developed in-house. As a result, we believe our systems
are flexible enough to upgrade or change software as new, improved third-party
software products are developed or as we develop our own new software.
 
     Our on-line architecture was also designed to be able to expand easily and
efficiently as usage grows. By treating the core backoffice technologies as
system "objects," we have constructed a natural environment for simply adding
additional copies of specific servers, as needed, to share the load. Besides
load sharing and usage expansion, this setup also provides natural failover
capabilities for the system. Any given server can suffer a problem and one or
several backups share the load while the problem is corrected.
 
     The OneSource on-line site is located at a dedicated hosting facility
managed by GTE/BBN Internetworking. It is a node on the GTE/BBN Internet
backbone. The system is available 24
 
                                       40
<PAGE>   42
 
hours a day, seven days a week. For more information, see "Risk Factors--If our
Website service is disrupted, our business would be adversely affected."
 
     The engineering team closely monitors the usage, delivery performance and
availability of the system. Particular attention is paid to individual product
usage, relative levels of customer activity, speed of data retrieval and
delivery, peak usage figures, uptime statistics and power requirements. This
engineering team is key to maintaining continuous service for our customers.
 
COMPETITION
 
     The business information services industry is intensely competitive. We
face direct or indirect competition from the following types of companies:
 
        - large, well-established business and financial information providers
          such as Dow Jones, Dialog, Lexis-Nexis, Pearson, Reuters, Thomson,
          Primark and McGraw-Hill
 
        - on-line information services or Websites targeted to specific markets
          or applications, such as NewsEdge, Factset and Bloomberg
 
        - providers of sales, marketing and credit information such as Dun &
          Bradstreet
 
        - Web retrieval, other Web "portal" companies and other free or low-cost
          mass market on-line services such as Excite, Infoseek, Lycos, Yahoo!
          and AOL/Netscape
 
     Many of our existing competitors, as well as a number of prospective
competitors, have longer operating histories, greater name recognition, larger
customer bases and significantly greater financial, technical and marketing
resources than we do. Certain of our competitors offer financial and business
information free of charge with the goal of achieving high enough usage to
facilitate the sale of substantial amounts of advertising. To the extent these
types of competitors offer products free of charge that are similar to ours, it
would have a material adverse impact on our business, financial condition and
results of operations. In addition, there are relatively low barriers to entry
to the Web-based information market and we may face additional competition from
new entrants. For more information, see "Risk Factors--We face intense
competition from other companies."
 
     The principal competitive factors in our industry are availability of
comprehensive and integrated business and financial information, ease of use,
support and training required and price/performance characteristics. We believe
that Business Browser products are differentiated from the products offered by
other providers because of our ability to deliver information from many
different, competing providers on an enterprise-wide basis. We also believe that
our focus on integrating and presenting information so that interpretation,
manipulation and analysis can be performed more easily also differentiates our
products.
 
EMPLOYEES
 
     We had 166 full-time employees as of December 31, 1998, including 67 in
sales and marketing, 22 in engineering, 14 in production/on-line support, 25 in
finance and administration and 38 on our Global Strategic Web Applications Team.
Our employees are not represented by any collective bargaining organization. We
have never experienced a work stoppage and we believe our relationships with our
employees are good.
 
                                       41
<PAGE>   43
 
FACILITIES
 
     Our corporate headquarters are located in a 28,766 square foot rented
facility in Cambridge, Massachusetts, under a lease expiring in July 1999. We
have entered into a new lease for a new, 35,766 square foot headquarters
facility in Concord, Massachusetts. We intend to move to that facility in June
1999. Our lease to the new facility expires in May 2004. We lease additional
sales offices in Chicago, New York, Los Angeles, San Francisco and London,
England. We believe that these facilities and additional or alternative space
available to us will be adequate to meet our needs for the foreseeable future.
 
LITIGATION
 
     OneSource is not a party to any material legal proceedings.
 
                                       42
<PAGE>   44
 
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
 
     The following table sets forth certain information with respect to the
executive officers and directors of OneSource as of March 1, 1999.
 
<TABLE>
<CAPTION>
                              AGE                          POSITION
NAME                          ---                          --------
<S>                           <C>   <C>
Martin Kahn(1)(2)...........  48    Chairman of the Board of Directors
Daniel J. Schimmel..........  39    President, Chief Executive Officer and Director
James A. Becker.............  41    Vice President, Global Strategic Web Applications Team
Philip J. Garlick...........  37    Vice President, Global Enterprise Sales and Marketing
Mark C. VanDine.............  42    Vice President, Engineering
Roy D. Landon...............  43    Vice President, Finance and Administration
David Dominik(1)............  42    Director
Gregg S. Newmark(2).........  40    Director
</TABLE>
 
------------
(1) Member of Compensation Committee.
 
(2) Member of Audit Committee.
 
     Martin Kahn joined OneSource as Chairman of the Board of Directors in
September 1993. Mr. Kahn has served as managing director of Cadence Information
Associates LLC since 1996. Mr. Kahn was the chairman of Ovid Technologies, Inc.,
a producer of medical, scientific and technical CD Rom and network products,
from 1990 to 1998, was chairman of VISTA Information Solutions, Inc., a supplier
of information about geographically-based risk, from 1992 to 1996 and was
chairman of Shoppers Express, Inc., an Internet-based grocery shopping service,
from 1995 to 1998. Mr. Kahn holds an MBA from the Harvard Business School and a
B.A. from Yale University.
 
     Daniel J. Schimmel joined OneSource as President, Chief Executive Officer
and a Director in 1993. Prior to joining OneSource, Mr. Schimmel served as
general manager of the OneSource Division and held other operating positions at
Lotus. Mr. Schimmel holds an MBA from the Harvard Business School and a B.A.
from Harvard University.
 
     James A. Becker joined OneSource as the Director of Product Management in
1993 and became Vice President, Global Strategic Web Applications Team in 1995.
Prior to joining OneSource, Mr. Becker served as group product manager at Lotus.
Mr. Becker holds an MBA from the Yale School of Management and a B.A. from Brown
University.
 
     Philip J. Garlick joined OneSource as Director of Marketing and Product
Development in 1993, served as Vice President and General Manager Europe from
1995 to October 1997, and in October 1997 became Vice President, Global
Enterprise Sales and Marketing. Prior to joining OneSource, Mr. Garlick was a
marketing executive at Lotus UK. Mr. Garlick holds an MA in Economics and a B.A.
from Manchester University.
 
     Mark C. VanDine joined OneSource as Senior Product Manager in 1993, served
as Director, Platform Product Management in 1995 and in 1996 became Vice
President, Engineering. Prior to joining OneSource, Mr. VanDine was a senior
consultant at Lotus. Mr. VanDine holds a B.A. and an MBA from Penn State
University.
 
                                       43
<PAGE>   45
 
     Roy D. Landon joined OneSource as Director, Finance and Administration in
1993 and became Vice President, Finance and Administration in 1997. Prior to
joining OneSource, Mr. Landon was director of plans and controls for the
Consulting and Information Services Group at Lotus. Mr. Landon holds a B.S. from
Babson College.
 
     David Dominik joined OneSource as a Director in 1993. Mr. Dominik has been
a managing director at Bain Capital Inc. since January 1990. He is also a
director of Oacis Healthcare Holdings Corp., a clinical information systems
software company.
 
     Gregg S. Newmark joined OneSource as a Director in 1993. Since 1993 Mr.
Newmark has served as general partner of William Blair Venture Partners, as a
principal of William Blair & Company, L.L.C. and as a managing director of
William Blair Capital Partners.
 
ELECTION OF OFFICERS AND DIRECTORS
 
     The executive officers of OneSource are elected by the Board of Directors
on an annual basis and serve until their successors are duly elected and
qualified. Messrs. Dominik and Newmark were selected as directors of OneSource
pursuant to a Stockholders Agreement dated September 8, 1993 between OneSource
and certain of its stockholders, which agreement will terminate as of the
effective date of this offering. For more information, see "Certain
Transactions." There are no family relationships among any of the executive
officers or directors of OneSource.
 
COMMITTEES OF THE BOARD OF DIRECTORS
 
     The Board of Directors has appointed a Compensation Committee consisting of
Messrs. Kahn and Dominik. The Compensation Committee reviews and evaluates the
compensation and benefits of all officers of OneSource, reviews general policy
matters relating to compensation and benefits of OneSource employees and make
recommendations concerning these matters to the Board of Directors. The
Compensation Committee also administers OneSource's stock option and stock
purchase plans. For more information, see "--Equity Plans."
 
     The Board of Directors has also appointed an Audit Committee consisting of
Messrs. Kahn and Newmark. The Audit Committee reviews, with OneSource's
independent auditors, the scope and timing of their audit services and any other
services they are asked to perform, the auditors' report on OneSource's
consolidated financial statements following completion of their audit, and
OneSource's policies and procedures with respect to internal accounting and
financial controls. In addition, the Audit Committee will make annual
recommendations to the Board of Directors for the appointment of independent
auditors for the ensuing year.
 
DIRECTOR COMPENSATION
 
     Directors who are not employees of OneSource and who are not affiliated
with principal stockholders (also referred to as "outside directors"), will
receive an annual retainer fee and a fee for attending regular (or special)
meetings of the Board of Directors and for meetings of any committees of the
Board of Directors on which they serve, if such meetings are held separately.
Currently, Mr. Kahn is the only outside director. Outside directors also are
eligible to participate in OneSource's 1999 Stock Option and Incentive Plan.
Directors also are reimbursed for reasonable out-of-pocket expenses incurred in
attending such meetings. For more information, see "--Equity Plans," and
"Certain Transactions."
 
                                       44
<PAGE>   46
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
     The Compensation Committee is comprised of Messrs. Kahn and Dominik.
Neither member of the Compensation Committee serves as a member of the board of
directors or compensation committee of any entity that has one or more executive
officers serving as a member of OneSource's Board of Directors or Compensation
Committee.
 
EXECUTIVE COMPENSATION
 
  Summary Compensation
 
     The following table sets forth the compensation earned by (a) the Chief
Executive Officer and (b) OneSource's four other most highly compensated
executive officers (together with the Chief Executive Officer, the "Named
Executive Officers") for services rendered in all capacities to OneSource during
the year ended December 31, 1998.
 
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                  ANNUAL COMPENSATION(1)
                                                  -----------------------       ALL OTHER
          NAME AND PRINCIPAL POSITION               SALARY        BONUS      COMPENSATION(2)
          ---------------------------             ----------    ---------    ---------------
<S>                                               <C>           <C>          <C>
Daniel J. Schimmel..............................   $164,997      $57,749              --
  President and Chief Executive Officer
James A. Becker.................................    123,748       24,750              --
  Vice President, Global Strategic Web
  Applications Team
Philip J. Garlick...............................    144,000       47,520        $145,725
  Vice President, Global Enterprise Sales and
  Marketing
Mark C. VanDine.................................    115,498       23,100              --
  Vice President, Engineering
Roy D. Landon...................................    105,186       21,037              --
  Vice President, Finance and Administration
</TABLE>
 
------------
(1) OneSource did not make any restricted stock awards, grant any stock
    appreciation rights or make any long-term incentive payments during 1998 to
    its executive officers. Options granted to the Named Executive Officers were
    granted at fair market value as determined by the Board of Directors based
    on all factors available to them on the grant date.
 
(2) Mr. Garlick received additional compensation in connection with his
    relocation from the UK to Massachusetts, including car and housing
    allowances, moving expenses and payment of certain taxes.
 
  Option Grants in Last Fiscal Year
 
     None of the Named Executive Officers were granted options in the year ended
December 31, 1998.
 
                                       45
<PAGE>   47
 
  Option Exercises and Year-End Holdings
 
     The following table sets forth information concerning stock option
exercises during 1998 by each of the Named Executive Officers and the number and
value of unexercised options held by them as of December 31, 1998.
 
      AGGREGATE OPTION EXERCISES IN 1998 AND FISCAL YEAR-END OPTION VALUES
 
<TABLE>
<CAPTION>
                                                                  NUMBER OF SECURITIES          VALUE OF UNEXERCISED
                                                                 UNDERLYING UNEXERCISED         IN-THE-MONEY OPTIONS
                                     SHARES                    OPTIONS AT FISCAL YEAR-END       AT FISCAL YEAR-END(1)
                                   ACQUIRED ON      VALUE      ---------------------------   ---------------------------
              NAME                  EXERCISE     REALIZED(1)   EXERCISABLE   UNEXERCISABLE   EXERCISABLE   UNEXERCISABLE
              ----                 -----------   -----------   -----------   -------------   -----------   -------------
<S>                                <C>           <C>           <C>           <C>             <C>           <C>
Daniel J. Schimmel...............         0              --      506,732              0                         $0
  President and Chief Executive
  Officer
James A. Becker..................    22,000                      122,000        100,000
  Vice President, Global
    Strategic
  Web Applications Team
Philip J. Garlick................         0              --       67,600        110,000
  Vice President, Global
    Enterprise
  Sales and Marketing
Mark C. VanDine..................         0              --       78,000         60,000
  Vice President, Engineering
Roy D. Landon....................         0              --       52,000         20,000
  Vice President, Finance and
  Administration
</TABLE>
 
------------
(1) There was no public trading market for the common stock as of December 31,
    1998. Accordingly, these values have been calculated by determining the
    difference between the assumed initial public offering price of $        per
    share and the exercise price of the Named Executive Officer's options.
 
EQUITY PLANS
 
     1999 Stock Option and Incentive Plan.  OneSource's 1999 Stock Option and
Incentive Plan (the "1999 Stock Option Plan") was adopted by the Board of
Directors in February 1999 and approved by OneSource's stockholders in
             , 1999, to be effective upon the completion of this offering. The
1999 Stock Option Plan provides for the grant of stock-based awards to
employees, officers and directors of, and consultants or advisors to, OneSource.
Under the 1999 Stock Option Plan, OneSource may grant options that are intended
to qualify as incentive stock options ("incentive stock options") within the
meaning of Section 422 of the Internal Revenue Code of 1986, as amended (the
"Code"), options not intended to qualify as incentive stock options
("non-qualified stock options"), restricted stock and other stock-based awards.
Incentive stock options may be granted only to employees of OneSource. A total
of 800,000 shares of common stock may be issued upon the exercise of options or
other awards granted under the 1999 Stock Option Plan after the completion of
this offering. The maximum number of shares with respect to which awards may be
granted to any employee under the 1999 Stock Option Plan shall not exceed
100,000 shares of common stock during any calendar year.
 
     The 1999 Stock Option Plan is administered by the Board of Directors and
the Compensation Committee. Subject to the provisions of the 1999 Stock Option
Plan, each of the Board of Directors and the Compensation Committee has the
authority to select the persons to
 
                                       46
<PAGE>   48
 
whom awards are granted and determine the terms of each award, including the
number of shares of common stock subject to the award. Payment of the exercise
price of an award may be made in cash, shares of common stock, a combination of
cash and stock, a promissory note or by any other method approved by the Board
or Compensation Committee, consistent with Section 422 of the Code and Rule
16b-3 under the Exchange Act. Unless otherwise permitted by the Board of
Directors, awards are not assignable or transferable except by will or the laws
of descent and distribution, and, during the participant's lifetime, may be
exercised only by the participant.
 
     The Board of Directors or Compensation Committee may, in its sole
discretion, amend, modify or terminate any award granted or made under the 1999
Stock Option Plan, so long as such amendment, modification or termination would
not materially and adversely affect the participant. The Board of Directors or
Compensation Committee may also, in its sole discretion, accelerate or extend
the date or dates on which all or any particular option or options granted under
the 1999 Stock Option Plan may be exercised.
 
     1993 Stock Purchase and Option Plan.  OneSource's 1993 Stock Purchase and
Option Plan (the "1993 Plan") was adopted by the Board of Directors and approved
by OneSource's stockholders in September 1993. Under the 1993 Plan, OneSource is
authorized to grant incentive stock options and non-qualified stock options to
employees, consultants, directors and advisors of OneSource. The aggregate
number of shares of common stock which may be issued under the 1993 Plan is
2,100,000 shares and the aggregate number of shares of Class P common stock that
may be issued under the 1993 Plan is 20,000 shares. In February 1999, the Board
of Directors, voted to terminate the 1993 Plan effective immediately prior to
the closing of this offering.
 
     To date, OneSource has granted stock options to purchase an aggregate of
1,940,548 shares of common stock pursuant to the 1993 Plan.
 
     1999 Employee Stock Purchase Plan.  The 1999 Employee Stock Purchase Plan
(the "1999 Purchase Plan") was adopted by the Board of Directors in February
1999 and approved by OneSource's stockholders in                 1999, to be
effective upon the completion of this offering. The 1999 Purchase Plan provides
for the issuance of a maximum of 100,000 shares of common stock after the
completion of this offering.
 
     The 1999 Purchase Plan is administered by the Compensation Committee of the
Board of Directors. All employees of OneSource whose customary employment is for
more than 20 hours per week and for more than three months in any calendar year
and who have completed more than 180 days of employment with OneSource on or
before the first day of any Payment Period (as defined below) are eligible to
participate in the 1999 Purchase Plan. Employees who would own 5% or more of the
total combined voting power or value of OneSource's stock immediately after the
grant may not participate in the 1999 Purchase Plan. To participate in the 1999
Purchase Plan, an employee must authorize OneSource to deduct an amount (not
less than one percent nor more than 10 percent of a participant's total cash
compensation) from his or her pay during six-month payment periods (each, a
"Payment Period"). The first Payment Period will commence upon the registration
of OneSource's common stock under the Exchange Act and will end on the earlier
of the following                 or                 . Thereafter, the Payment
Periods will commence on the six-month periods commencing on                 1
and                 1, respectively, and ending on the following
                and                 ,
 
                                       47
<PAGE>   49
 
respectively, of each year, but in no case shall an employee be entitled to
purchase more than                 shares in any one Payment Period. The
exercise price for the option granted in each Payment Period is 85% of the
lesser of the average market price of the common stock on the first or last
business day of the Payment Period, in either event rounded up to the nearest
cent to avoid fractions of a dollar other than  1/4, 1/2 and  3/4. If an
employee is not a participant on the last day of the Payment Period, such
employee is not entitled to exercise his or her option, and the amount of his or
her accumulated payroll deductions will be refunded. Options granted under the
1999 Purchase Plan may not be transferred or assigned. An employee's rights
under the 1999 Purchase Plan terminate upon his or her voluntary withdrawal from
the plan at any time or upon termination of employment. No options have been
granted to date under the 1999 Purchase Plan.
 
401(K) PLAN
 
     OneSource has established a tax-qualified employee savings and retirement
plan. Employees must complete three months of service at OneSource before they
are eligible to participate on the first day of the month following the
completion. Employees may contribute a percentage of their pre-tax compensation
and OneSource may, in its discretion from year-to-year, make matching
contributions to the employees. Amounts matched by OneSource vest over three
years.
 
LIMITATION OF LIABILITY AND INDEMNIFICATION OF OFFICERS AND DIRECTORS
 
     OneSource's Restated Certificate of Incorporation and Amended and Restated
By-Laws provide that the directors and officers of OneSource shall be
indemnified by OneSource to the fullest extent authorized by Delaware law, as it
now exists or may in the future be amended, against all expenses and liabilities
reasonably incurred in connection with their service for or on behalf of
OneSource. In addition, the Restated Certificate of Incorporation provides that
the directors of OneSource will not be personally liable for monetary damages to
OneSource for breaches of their fiduciary duty as directors, unless they
violated their duty of loyalty to OneSource or its stockholders, acted in bad
faith, knowingly or intentionally violated the law, authorized illegal dividends
or redemptions or derived an improper personal benefit from their action as
directors. OneSource intends to obtain insurance which insures the directors and
officers of OneSource against certain losses and which insures OneSource against
certain of its obligations to indemnify such directors and officers.
 
                                       48
<PAGE>   50
 
                              CERTAIN TRANSACTIONS
 
     In connection with the management buy-out from Lotus in 1993, each of
William Blair Venture Partners III Limited Partnership and Information Partners
Capital Fund, L.P. and its affiliated entities purchased 162,000 shares of Class
P common stock for $1.62 million, or $10.00 per share, and 1,458,000 shares of
common stock for $180,000, or $0.12 per share. The shares of common stock held
by William Blair Venture Partners and Information Partners Capital are subject
to registration rights entitling the holder to demand that OneSource register
the shares under the Securities Act in certain circumstances to enable the
holder to resell its shares. For more information, see "Shares Eligible For
Future Sale." A Stockholders Agreement among OneSource, William Blair Venture
Partners, Information Partners Capital and certain other stockholders provides
that, for so long as William Blair Venture Partners or Information Partners
Capital continues to own at least 25% of the common stock which each such entity
originally purchased in the buy-out, OneSource shall cause a representative of
each of William Blair Venture Partners and Information Partners Capital to be
nominated to the Board of Directors. Mr. Newmark, a general partner of William
Blair Venture Management Company (the general partner of William Blair Venture
Partners), currently serves as the William Blair Venture Partners representative
and Mr. Dominik, a general partner of Information Partners, Inc. (the general
partner of Information Partners Capital), currently serves as the Information
Partners Capital representative. The Stockholders Agreement will be terminated
upon consummation of this offering.
 
     Since 1993, OneSource has paid each of William Blair Venture Partners and
an affiliate of Information Partners Capital an annual management fee of $0.1
million, pursuant to an oral arrangement. OneSource has agreed to pay each of
these entities a one-time fee of $0.5 million to terminate the management fee
arrangement.
 
     OneSource intends to use approximately $6.7 million of its net proceeds
from this offering to repay a note issued by OneSource to Lotus in connection
with the purchase of OneSource's business from Lotus in 1993. The note bears
interest at the rate of 8% per year and is due September 8, 2000, unless
accelerated upon certain events. The completion of this offering would require
OneSource to repay a significant portion of the note if it is not repaid in
full.
 
                                       49
<PAGE>   51
 
                       PRINCIPAL AND SELLING STOCKHOLDERS
 
     The following table sets forth certain information known to OneSource
regarding beneficial ownership of OneSource's common stock as of March 1, 1999
and as adjusted to reflect the sale of the shares of common stock in this
offering by (a) each person known by OneSource to be the beneficial owner of
more than 5% of OneSource's common stock; (b) each of OneSource's directors; (c)
each Named Executive Officer (for more information, see "Management--Executive
Compensation"); (d) all executive officers and directors as a group; and (e)
each selling stockholder. Unless otherwise indicated, to the knowledge of
OneSource, each stockholder possesses sole voting and investment power with
respect to the shares listed, except to the extent an individual stockholder's
shares are owned jointly with that person's spouse.
 
<TABLE>
<CAPTION>
                                            SHARES BENEFICIALLY                 SHARES BENEFICIALLY
                                            OWNED PRIOR TO THE                    OWNED AFTER THE
                                                OFFERING(1)                       OFFERING(1)(2)
                                            -------------------                 -------------------
                                            NUMBER OF               SHARES      NUMBER OF
 NAME AND ADDRESS OF BENEFICIAL OWNER(3)     SHARES     PERCENT   OFFERED(2)     SHARES     PERCENT
 ---------------------------------------    ---------   -------   -----------   ---------   -------
<S>                                         <C>         <C>       <C>           <C>         <C>
Information Partners Capital Fund,
  L.P.(4).................................  1,619,999    44.0%
William Blair Venture Partners III Limited
  Partnership(5)..........................  1,620,000    44.0
Martin Kahn(6)............................    329,364     8.4
Daniel J. Schimmel(7).....................    586,732    14.0
James A. Becker(8)........................    166,000     4.5
Philip J. Garlick(9)......................     71,600     1.9
Mark C. Van Dine(10)......................     86,000     2.3
Roy D. Landon(11).........................     60,000     1.6
David Dominik(4)..........................  1,619,999    44.0
Gregg Newmark(5)..........................  1,620,000    44.0
Lotus Development Corporation(12).........    200,000     5.2
All executive officers and directors as a
  group (8 persons)(13)...................  4,539,695    95.4
</TABLE>
 
------------
 (1) Based on         shares of common stock outstanding prior to the offering
     and         outstanding upon completion of the offering. The number of
     shares of common stock deemed outstanding includes (a) one share of common
     stock for each share of outstanding Class P common stock and (b) shares
     issuable pursuant to options held by the respective person or group which
     may be exercised within 60 days after March 1, 1999 ("presently exercisable
     stock options"), as set forth in the other footnotes to this table,
     including options to purchase             shares that are being exercised
     by certain of the selling stockholders in connection with this offering.
     For purposes of calculating each person's or group's percentage ownership,
     presently exercisable stock options are included for that person or group
     but not the presently exercisable stock options of any other person or
     group.
 
 (2) Assumes that the Underwriters' over-allotment option to purchase up to an
     additional             shares from the selling stockholders is not
     exercised. If the Underwriters exercise their over-allotment option to
     purchase up to an additional             shares, then the following
     stockholders will sell up to the following number of additional shares:
 
 (3) For more information, see "Management--Executive Officers and Directors."
     Unless otherwise indicated, the address for each beneficial owner is c/o
     OneSource Information Services, Inc., 150 CambridgePark Drive, Cambridge,
     MA 02140.
 
 (4) Includes 55,933 shares owned by BCIP Associates and 60,613 shares owned by
     BCIP Trust Associates, L.P. The respective general partners of these
     entities, including Mr. Dominik, exercise sole voting and investment power
     with respect to the shares owned by such entities. Each of these persons
     disclaims beneficial ownership of such shares except to the extent of his
     respective proportionate pecuniary interest therein.
 
                                       50
<PAGE>   52
 
 (5) The general partners of this entity, including Mr. Newmark, exercise sole
     voting and investment power with respect to the shares owned by such
     entity. Each of these persons disclaims beneficial ownership of such shares
     except to the extent of his respective proportionate pecuniary interest
     therein.
 
 (6) Includes 249,364 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
 (7) Includes 506,732 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
 (8) Includes 122,000 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
 (9) Includes 67,600 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
(10) Includes 78,000 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
(11) Includes 52,000 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
(12) Lotus Development Corporation's address is 55 Cambridge Parkway, Cambridge,
     MA 02142. All of such shares are issuable pursuant to a currently
     exercisable warrant.
 
(13) Please reference notes 5 through 11 inclusive. Includes 1,075,696 shares of
     common stock issuable pursuant to stock options that are exercisable within
     60 days of March 1, 1999.
 
                          DESCRIPTION OF CAPITAL STOCK
 
     Effective upon the closing of this offering and the filing of OneSource's
Restated Certificate of Incorporation, the authorized capital stock of OneSource
will consist of 20,000,000 shares of common stock, par value $.01 per share, and
1,000,000 shares of preferred stock, par value $.01 per share.
 
     Prior to the closing of this offering and in accordance with OneSource's
Certificate of Incorporation as currently in effect, OneSource is authorized to
issue up to 6,500,000 shares of common stock, par value $.01 per share, of which
3,329,392 shares are issued and outstanding and 500,000 shares of Class P common
stock, par value $.01 per share, of which 352,400 shares are issued and
outstanding. Prior to the closing of this offering, all shares of Class P common
stock and preference amount thereon will be reclassified into            shares
of common stock.
 
     The following summary description of OneSource's capital stock is not
intended to be complete and is qualified by reference to the provisions of
applicable law and to OneSource's Restated Certificate of Incorporation and
Amended and Restated By-laws filed as exhibits to the registration statement of
which this prospectus is a part.
 
COMMON STOCK
 
     As of March 1, 1999, there were 3,329,392 shares of common stock
outstanding held by 42 stockholders of record. Based upon the number of shares
outstanding as of that date and giving effect to the issuance of the
                shares of common stock offered by OneSource in this offering and
the reclassification of each outstanding share of Class P common stock into one
share of common stock plus an additional number of shares of common stock
determined by dividing the preference amount for such shares by the assumed
initial public offering price of $        per share and the repurchase of
such           additional shares of common stock by OneSource, there will be
                shares of common stock outstanding upon the closing of this
offering. In addition, as of              , 1999, there were outstanding stock
options for the purchase of a total of                 shares of common stock
and outstanding warrants for the purchase of         shares of common stock.
 
                                       51
<PAGE>   53
 
     Holders of common stock are entitled to one vote for each share held on all
matters submitted to a vote of stockholders and do not have cumulative voting
rights. Directors are elected by a plurality of the votes of the shares present
in person or by proxy at the meeting and entitled to vote in such election.
Holders of common stock are entitled to receive ratably such dividends, if any,
as may be declared by the Board of Directors out of funds legally available
therefor, subject to any preferential dividend rights of outstanding preferred
stock. Upon the liquidation, dissolution or winding up of OneSource, the holders
of common stock are entitled to receive ratably the net assets of OneSource
available after the payment of all debts and other liabilities of OneSource,
subject to the prior rights of any outstanding preferred stock. Holders of the
common stock have no preemptive, subscription, redemption or conversion rights,
nor are they entitled to the benefit of any sinking fund. The outstanding shares
of common stock are, and the shares offered by OneSource in this offering will
be, when issued and paid for, validly issued, fully paid and nonassessable. The
rights, powers, preferences and privileges of holders of common stock are
subject to, and may be adversely affected by, the rights of the holders of
shares of any series of preferred stock which OneSource may designate and issue
in the future.
 
PREFERRED STOCK
 
     The Board of Directors will be authorized, subject to any limitations
prescribed by law, without further stockholder approval, to issue from time to
time up to an aggregate of 1,000,000 shares of preferred stock, in one or more
series. Each such series of preferred stock shall have such number of shares,
designations, preferences, voting powers, qualifications and special or relative
rights or privileges as shall be determined by the Board of Directors, which may
include, among others, dividend rights, voting rights, redemption and sinking
fund provisions, liquidation preferences, conversion rights and preemptive
rights.
 
     The stockholders of OneSource have granted the Board of Directors authority
to issue the preferred stock and to determine its rights and preferences in
order to eliminate delays associated with a stockholder vote on specific
issuances. The rights of the holders of common stock will be subject to the
rights of holders of any preferred stock issued in the future. The issuance of
preferred stock, while providing desirable flexibility in connection with
possible acquisitions and other corporate purposes, could adversely affect the
voting power or other rights of the holders of common stock, and could make it
more difficult for a third-party to acquire, or discourage a third-party from
attempting to acquire, a majority of the outstanding voting stock of OneSource.
OneSource has not, to date, issued any shares of preferred stock and has no
present plans to issue any shares of preferred stock.
 
DELAWARE LAW AND CERTAIN CHARTER AND BY-LAW PROVISIONS; ANTI-TAKEOVER EFFECTS
 
     Upon completion of this offering, OneSource will be subject to the
provisions of Section 203 of the General Corporation Law of Delaware. Section
203 prohibits a publicly-held Delaware corporation from engaging in a "business
combination" with an "interested stockholder" for a period of three years after
the date of the transaction in which the person became an interested
stockholder, unless the business combination is approved in a prescribed manner.
A "business combination" includes mergers, asset sales and other transactions
resulting in a financial benefit to the interested stockholder. Subject to
certain exceptions, an "interested stockholder" is a person who, together with
affiliates and associates, owns, or within the prior three years did own, 15% or
more of the corporation's outstanding voting stock.
 
                                       52
<PAGE>   54
 
     The Restated Certificate of Incorporation provides that directors may be
removed only for cause by the affirmative vote of the holders of 75% of the
shares of capital stock of OneSource entitled to vote. In addition, under the
Restated Certificate of Incorporation any vacancy on the Board of Directors,
however occurring, including a vacancy resulting from an enlargement of the
Board, may only be filled by vote of a majority of the directors then in office.
The likely effect of the limitations on the removal of directors and filling of
vacancies is an increase in the time required for the stockholders to change the
composition of the Board of Directors.
 
     The Restated By-Laws to be adopted upon the closing of this offering
provide that any action required or permitted to be taken by the stockholders of
OneSource at an annual meeting or special meeting of stockholders may only be
taken if OneSource is given proper advance notice of the action. The Restated
By-Laws further provide that special meetings of stockholders may only be called
by a majority of the Board of Directors, the Chairman of the Board of Directors
or the President of OneSource. The foregoing provisions could have the effect of
delaying until the next stockholders meeting stockholder actions which are
favored by the holders of a majority of the outstanding voting securities of
OneSource. However, the Restated By-Laws provide that stockholders may take
action by written consent.
 
     The General Corporation Law of Delaware provides generally that the
affirmative vote of a majority of the shares entitled to vote on any matter is
required to amend a corporation's certificate of incorporation or by-laws,
unless a corporation's certificate of incorporation or by-laws, as the case may
be, requires a greater percentage. The Restated By-Laws require the affirmative
vote of the holders of at least 75% of the issued and outstanding shares of
capital stock of OneSource entitled to vote to amend or repeal any of the
foregoing provisions of the Restated By-Laws. The 75% stockholder vote would be
in addition to any separate class vote that might be required pursuant to the
terms of any series of preferred stock that might be outstanding at the time any
such amendments are submitted to stockholders.
 
TRANSFER AGENT AND REGISTRAR
 
     The transfer agent and registrar for the common stock will be
                .
 
                                       53
<PAGE>   55
 
                        SHARES ELIGIBLE FOR FUTURE SALE
 
     Upon completion of this offering, OneSource will have
shares of common stock outstanding (assuming no exercise of the outstanding
options or warrants). Of these shares, the                 shares
(                shares if the over-allotment option is exercised in full) to be
sold in this offering will be freely tradable without restriction or further
registration under the Securities Act, except that any shares purchased by
affiliates of OneSource, as that term is defined in Rule 144 under the
Securities Act ("Affiliates"), may generally only be sold in compliance with the
limitations of Rule 144 described below.
 
SALES OF RESTRICTED SHARES
 
     The remaining                 shares of common stock outstanding upon
completion of this offering are deemed "Restricted Shares" under Rule 144 or
Rule 701 under the Securities Act. Approximately                 of such
Restricted Shares will be eligible for sale in the public market pursuant to
Rule 144(k) on the date of this prospectus. Upon expiration of certain lock-up
agreements, 180 days after the date of this prospectus, an additional
                shares of common stock will be eligible for sale in the public
market pursuant to Rule 144 under the Securities Act.
 
     In general, under Rule 144, a person (or persons whose shares are
aggregated), including an Affiliate, who has beneficially owned Restricted
Shares for at least one year is entitled to sell, within any three-month period,
a number of such shares that does not exceed the greater of (a) one percent of
the then outstanding shares of common stock (approximately         shares
immediately after this offering) or (b) the average weekly trading volume in the
common stock in the over-the-counter market during the four calendar weeks
preceding the date on which notice of such sale is filed, provided certain
requirements concerning availability of public information, manner of sale and
notice of sale are satisfied. In addition, Affiliates must comply with the
restrictions and requirements of Rule 144, other than the one-year holding
period requirement, in order to sell shares of common stock which are not
Restricted Shares. Under Rule 144(k), a person who is not an Affiliate and has
not been an Affiliate for at least three months prior to the sale and who has
beneficially owned Restricted Shares for at least two years may resell such
shares without compliance with the foregoing requirements. In meeting the one-
and two-year holding periods described above, a holder of Restricted Shares can
include the holding periods of a prior owner who was not an Affiliate. The one-
and two-year holding periods described above do not begin to run until the full
purchase price or other consideration is paid by the person acquiring the
Restricted Shares from the issuer or an Affiliate. Rule 701 provides that
currently outstanding shares of common stock acquired under OneSource's employee
compensation plans may be resold by persons, other than Affiliates, beginning 90
days after the date of this prospectus, subject only to the manner of sale
provisions of Rule 144, and by Affiliates under Rule 144, without compliance
with its one-year minimum holding period, subject to certain limitations.
 
OPTIONS
 
     Rule 701 also provides that the shares of common stock acquired upon the
exercise of currently outstanding options or pursuant to other rights granted
under OneSource's stock plans may be resold by persons, other than Affiliates,
beginning 90 days after the date of this prospectus, subject only to the manner
of sale provisions of Rule 144, and by Affiliates under
 
                                       54
<PAGE>   56
 
Rule 144, without compliance with its one-year minimum holding period, subject
to certain limitations. As of the date of this prospectus, the Board of
Directors has authorized an aggregate of up to                 shares of common
stock for issuance pursuant to OneSource's stock option and stock purchase
plans. At the date of this prospectus,                 shares of common stock
are issuable pursuant to outstanding vested options or pursuant to other rights
granted under OneSource's stock plan(s), of which approximately
                shares are not subject to lock-up agreements with the
Underwriters and will be eligible for sale in the public market in accordance
with Rule 701 under the Securities Act beginning 90 days after the date of this
prospectus;                 shares of common stock are issuable pursuant to
outstanding options that are not yet exercisable; and                 shares of
common stock are available for future grants under OneSource's stock option and
stock purchase plans.
 
     OneSource intends to file one or more registration statements on Form S-8
under the Securities Act 180 days after the date of this prospectus to register
all shares of common stock which are issuable pursuant to OneSource's stock
option and stock purchase plans. Such registration statements are expected to
become effective upon filing. Shares covered by such registration statements
will thereupon be eligible for sale in the public markets.
 
LOCK-UP AGREEMENTS
 
     With certain exceptions, OneSource, its executive officers and directors,
the selling stockholders and certain other security-holders have agreed not to
sell or transfer any shares of common stock (or any security convertible into or
exchangeable or exercisable for common stock), or to engage in certain hedging
transactions with respect to the common stock without the prior written consent
of William Blair & Company, L.L.C. ("William Blair") for a period of 180 days
from the date of this prospectus. In addition, for a period of 180 days from the
date of this prospectus, except as required by law, OneSource has agreed that
its Board of Directors will not consent to any offer for sale, sale or other
disposition, or any transaction which is designed or could be expected to result
in the disposition by any person, directly or indirectly, of any shares of
common stock without the prior written consent of William Blair. For more
information, see "Underwriting." William Blair in its sole discretion at any
time or from time to time and without notice may release for sale in the public
market all or any portion of the shares subject to the lock-up agreements.
 
REGISTRATION RIGHTS
 
     Upon the expiration of the contractual lock-up period, certain security
holders of OneSource (the "Rights Holders") will be entitled to require
OneSource to register under the Securities Act up to a total of
                shares of outstanding common stock (the "Registrable Shares")
under the terms of an agreement between OneSource and the Rights Holders (the
"Registration Rights Agreement"). The Registration Rights Agreement provides
that if OneSource proposes to register in a firm commitment underwritten
offering any of its securities under the Securities Act at any time or times,
the Rights Holders, subject to certain exceptions, shall be entitled to include
Registrable Shares in such registration. However, the managing underwriter of
any such offering may exclude for marketing reasons some or all of such
Registrable Shares from such registration. The Rights Holders also have, subject
to certain conditions and limitations, the right to require OneSource, no more
than once in any six-month period, to prepare and file a registration statement
under the Securities Act with respect to their
 
                                       55
<PAGE>   57
 
Registrable Shares. OneSource is generally required to bear the expenses of all
such registrations, except underwriting discounts and commissions.
 
     Prior to this offering, there has been no public market for the common
stock of OneSource, and no predictions can be made as to the effect, if any,
that market sales of shares of common stock prevailing from time to time, or the
availability of shares for future sale, may have on the market price for our
common stock. Sales of substantial amounts of common stock, or the perception
that such sales could occur, could adversely affect prevailing market prices for
our common stock and could impair OneSource's future ability to obtain capital
through an offering of equity securities.
 
                                       56
<PAGE>   58
 
                                  UNDERWRITING
 
     Each Underwriter named below has agreed to purchase from OneSource and the
selling stockholders the number of shares of common stock set forth opposite its
name.
 
<TABLE>
<CAPTION>
                                                              NUMBER OF
                        UNDERWRITER                            SHARES
                        -----------                           ---------
<S>                                                           <C>
William Blair & Company, L.L.C. ............................
U.S. Bancorp Piper Jaffray Inc. ............................
Adams, Harkness & Hill, Inc. ...............................
                                                              --------
     Total..................................................
</TABLE>
 
     This offering will be underwritten on a firm commitment basis. In the
Underwriting Agreement among OneSource, the selling stockholders and the
Underwriters, the Underwriters have agreed, subject to the terms and conditions
set forth therein, to purchase the shares of common stock being sold pursuant
thereto at a price per share equal to the public offering price less the
underwriting discount specified on the cover page of this prospectus. According
to the terms of the Underwriting Agreement, the Underwriters will either
purchase all of the shares or none of them. In the event of default by any
Underwriter, in certain circumstances the purchase commitments of the
non-defaulting Underwriters may be increased or the Underwriting Agreement may
be terminated. William Blair, U.S. Bancorp Piper Jaffray Inc. and Adams,
Harkness & Hill, Inc. are acting as the representatives of the Underwriters.
 
     The representatives of the Underwriters have advised OneSource and the
selling stockholders that the Underwriters will offer the shares of common stock
to the public at the public offering price specified on the cover page of this
prospectus. The Underwriters may also offer the shares to certain dealers at the
public offering price less a concession of up to $     per share. The
Underwriters may allow, and these dealers may re-allow, a concession of up to
$     per share to certain other dealers. The Underwriters will offer the shares
subject to prior sale and subject to receipt and acceptance of the shares by the
Underwriters. The Underwriters may reject any order to purchase shares in whole
or in part. The Underwriters expect that OneSource and the selling stockholders
will deliver the shares to the Underwriters through the facilities of the
Depository Trust Company in New York, New York on or about              , 1999.
At that time, the Underwriters will pay OneSource and the selling stockholders
for the shares in immediately available funds. After the commencement of the
initial public offering, the representatives may change the offering price and
the other selling terms.
 
     The Underwriters have the option to purchase up to an aggregate of
                additional shares of common stock from the selling stockholders
at the same price they are paying for the                 shares offered hereby.
The Underwriters may purchase additional shares only to cover over-allotments
made in connection with this offering and only within 30 days after the date of
this prospectus. If the Underwriters decide to exercise this over-allotment
option, each Underwriter will be required to purchase additional shares in
approximately the same proportion as set forth in the table above. The
Underwriters will offer any additional shares that they purchase on the terms
described in the preceding paragraph.
 
                                       57
<PAGE>   59
 
     The following table summarizes the compensation to be paid by OneSource and
the selling stockholders to the Underwriters:
 
<TABLE>
<CAPTION>
                                                                         TOTAL
                                                     ---------------------------------------------
                                        PER SHARE    WITHOUT OVER-ALLOTMENT    WITH OVER-ALLOTMENT
                                        ---------    ----------------------    -------------------
<S>                                     <C>          <C>                       <C>
Public Offering Price.................
Underwriting Discount paid by
  OneSource...........................
Underwriting Discount paid by the
  selling stockholders................
</TABLE>
 
     OneSource estimates the expenses of this offering payable by OneSource
(excluding the underwriting discount) to be $           .
 
     OneSource and the selling stockholders have agreed to indemnify the
Underwriters and their controlling persons against certain liabilities,
including liabilities under the Securities Act.
 
     OneSource and certain stockholders of OneSource have agreed not to sell or
transfer any shares of common stock, or to engage in certain hedging
transactions with respect to the common stock, for a period of 180 days from the
date of this prospectus without the consent of William Blair, except in certain
limited circumstances. Stockholders who have agreed to this lock-up arrangement
hold an aggregate of                 shares of common stock and options to
purchase                 shares of common stock. For more information, see
"Shares Eligible for Future Sale."
 
     In connection with this offering, the Underwriters and other persons
participating in this offering may engage in transactions which affect the
market price of the common stock. These may include stabilizing and
over-allotment transactions and purchases to cover syndicate short positions.
Stabilizing transactions consist of bids or purchases for the purpose of
pegging, fixing or maintaining the price of the common stock. Over-allotment
involves selling more shares of common stock in this offering than are specified
on the cover page of this prospectus, which results in a syndicate short
position. The Underwriters may cover this short position by purchasing common
stock in the open market or by exercising all or part of their over-allotment
option. In addition, the representatives of the Underwriters may impose a
penalty bid. This allows the representatives to reclaim the selling concession
allowed to an Underwriter or selling group member if common stock sold by such
Underwriter or selling group member in this offering is repurchased by the
representatives in stabilizing or syndicate short covering transactions. These
transactions, which may be effected on the Nasdaq National Market, may
stabilize, maintain or otherwise affect the market price of the common stock and
could cause the price to be higher than it would be without these transactions.
The Underwriters and other participants in this offering are not required to
engage in any of these activities and may discontinue any of these activities at
any time without notice. Neither OneSource nor any of the Underwriters makes any
representation or prediction as to whether the Underwriters will engage in such
transactions or choose to discontinue any transactions engaged in or as to the
direction or magnitude of any effect that these transactions may have on the
price of the common stock.
 
     The representatives of the Underwriters have advised OneSource and the
selling stockholders that the Underwriters do not intend to confirm, without
client authorization, sales to any account over which they exercise
discretionary authority.
 
                                       58
<PAGE>   60
 
     Prior to this offering, there has been no public market for OneSource's
common stock. Consequently, OneSource, representatives of the selling
stockholders and the representatives of the Underwriters negotiated to determine
the initial public offering price. They considered current market conditions,
OneSource's operating results in recent periods, the market capitalization of
other companies in its industry, estimates of OneSource's potential and other
factors they deemed relevant. The estimated price range specified on the cover
page of this prospectus may change because of market conditions and other
factors.
 
     The Underwriters have reserved for sale, at the initial public offering
price, up to 5% of the shares of common stock in this offering for OneSource
employees and certain other individuals with a relationship with OneSource.
Purchases of the reserved shares would reduce the number of shares available for
sale to the general public. The Underwriters will offer any reserved shares
which are not so purchased to the general public on the same terms as the other
shares.
 
     OneSource intends to apply for quotation of the common stock on the Nasdaq
National Market under the symbol "ONES."
 
     Certain of the Underwriters and their affiliates engage in transactions
with, and perform services for, OneSource in the ordinary course of business and
have engaged, and may in the future engage, in commercial banking and investment
banking transactions with OneSource. In connection with rendering such services
in the past, the Underwriters and their affiliates have received customary
compensation.
 
     William Blair is an affiliate of William Blair Venture Partners. As such,
William Blair may be deemed to be an affiliate of OneSource under Schedule E of
the By-Laws of the National Association of Securities Dealers, Inc. ("NASD").
Mr. Newmark, a principal of William Blair, currently serves on OneSource's Board
of Directors as the representative of William Blair Venture Partners. In
addition, since 1993, OneSource has paid William Blair Venture Partners an
annual management fee of $100,000 pursuant to an oral arrangement and OneSource
will pay William Blair Venture Partners $500,000 upon the closing of this
offering in termination of this arrangement. For more information, see
"Principal and Selling Stockholders" and "Certain Transactions." When an NASD
member participates in an offering of an affiliated company's equity securities,
Rule 2720 of the NASD requires that a "qualified independent underwriter" within
the meaning of the Rule participate in the preparation of the registration
statement and prospectus for the offering and conduct due diligence as part of
such preparation. In addition, if a bona fide independent market does not exist
for the offered securities, the public offering price can be no higher than that
recommended by the qualified independent underwriter. U.S. Bancorp Piper Jaffray
Inc. has accepted the responsibility of acting as the "qualified independent
underwriter" with respect to this offering and, accordingly, the initial public
offering price specified on the cover page of this prospectus does not exceed
that recommended by U.S. Bancorp Piper Jaffray in its capacity as such.
 
                                 LEGAL MATTERS
 
     The validity of the shares of common stock to be issued in this offering
will be passed upon for OneSource by Testa, Hurwitz & Thibeault, LLP, Boston,
Massachusetts. Certain legal matters in connection with this offering will be
passed upon for the Underwriters by Sidley & Austin, Chicago, Illinois.
 
                                       59
<PAGE>   61
 
                                    EXPERTS
 
     The consolidated financial statements as of December 31, 1997 and 1998 and
for each of the three years in the period ended December 31, 1998 included in
this prospectus have been so included in reliance upon the report of
PricewaterhouseCoopers LLP, independent accountants, given on the authority of
said firm as experts in auditing and accounting.
 
                             ADDITIONAL INFORMATION
 
     OneSource has filed with the Commission a registration statement on Form
S-1 (including all amendments and exhibits thereto, the "Registration
Statement") under the Securities Act with respect to the common stock in this
offering. As permitted by the rules and regulations of the Commission, this
prospectus omits certain information contained in the Registration Statement.
For further information with respect to OneSource and the common stock offered
in this offering, you should refer to the Registration Statement and to the
exhibits and schedules filed as part thereof. Statements contained in this
prospectus regarding the contents of any agreement or other document filed as an
exhibit to the Registration Statement are not necessarily complete, and in each
instance reference is made to the copy of such agreement or document filed as an
exhibit to the Registration Statement, each such statement being qualified in
all respects by such reference. You may obtain copies of all or any portion of
the Registration Statement at prescribed rates from the public reference
facilities maintained by the Commission at Room 1024, Judiciary Plaza, 450 Fifth
Street, N.W., Washington, DC 20549, at its regional offices located at Seven
World Trade Center, New York, New York 10007 and 500 West Madison Street,
Chicago, Illinois 60661, or by calling the Commission at 1-800-SEC-0330. In
addition, the Commission maintains a Website that contains reports, proxy and
information statements and other information regarding registrants (including
OneSource) that file electronically with the Commission which can be accessed at
http://www.sec.gov.
 
     OneSource intends to furnish to its stockholders annual reports containing
consolidated financial statements audited by an independent public accounting
firm and with quarterly reports for each of the first quarters of each fiscal
year containing unaudited consolidated financial statements.
 
                                       60
<PAGE>   62
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                   INDEX TO CONSOLIDATED FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                              PAGE
                                                              ----
<S>                                                           <C>
Report of Independent Accountants...........................  F-2
Consolidated Balance Sheet as of December 31, 1997 and 1998
  and Pro Forma December 31, 1998 (unaudited)...............  F-3
Consolidated Statement of Operations for the Years Ended
  December 31, 1996, 1997 and 1998..........................  F-4
Consolidated Statement of Changes in Stockholders' Deficit
  for the Years Ended December 31, 1996, 1997 and 1998......  F-5
Consolidated Statement of Cash Flows for the Years Ended
  December 31, 1996, 1997 and 1998..........................  F-6
Notes to Consolidated Financial Statements..................  F-7
</TABLE>
 
                                       F-1
<PAGE>   63
 
                       REPORT OF INDEPENDENT ACCOUNTANTS
 
To the Board of Directors and Stockholders of
OneSource Information Services, Inc.
 
     In our opinion, the accompanying consolidated balance sheet and the related
consolidated statements of operations, of changes in stockholders' deficit and
of cash flows present fairly, in all material respects, the financial position
of OneSource Information Services, Inc. and its subsidiary at December 31, 1997
and 1998, and the results of their operations and their cash flows for each of
the three years in the period ended December 31, 1998 in conformity with
generally accepted accounting principles. These financial statements are the
responsibility of the Company's management; our responsibility is to express an
opinion on these financial statements based on our audits. We conducted our
audits of these statements in accordance with generally accepted auditing
standards which require that we plan and perform the audit to obtain reasonable
assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements, assessing the
accounting principles used and significant estimates made by management, and
evaluating the overall financial statement presentation. We believe that our
audits provide a reasonable basis for the opinion expressed above.
 
PRICEWATERHOUSECOOPERS LLP
 
Boston, Massachusetts
February 26, 1999
 
                                       F-2
<PAGE>   64
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                           CONSOLIDATED BALANCE SHEET
                       (IN THOUSANDS, EXCEPT SHARE DATA)
 
<TABLE>
<CAPTION>
                                                                 DECEMBER 31,        PRO FORMA
                                                              -------------------   DECEMBER 31,
                                                                1997       1998         1998
                                                              --------   --------   ------------
                                                                                      (NOTE 2)
                                                                                    (UNAUDITED)
                              ASSETS
<S>                                                           <C>        <C>        <C>
Current assets:
  Cash and cash equivalents.................................  $    341   $  8,665     $  8,665
  Accounts receivable, net of allowance for doubtful
     accounts of $210 and $300 at December 31, 1997 and
     1998, respectively.....................................     8,703      9,621        9,621
  Deferred subscription costs...............................     5,037      6,662        6,662
  Prepaid expenses and other current assets.................       323        426          426
                                                              --------   --------     --------
     Total current assets...................................    14,404     25,374       25,374
Property and equipment, net.................................     1,826      1,770        1,770
Restricted time deposit.....................................        --        100          100
Other assets................................................       414        402          402
                                                              --------   --------     --------
       Total assets.........................................  $ 16,644   $ 27,646     $ 27,646
                                                              ========   ========     ========
                LIABILITIES AND STOCKHOLDERS' DEFICIT
Current liabilities:
  Current portion of capital lease obligations..............  $    580   $    471     $    471
  Notes payable.............................................     1,530         --           --
  Accounts payable..........................................     1,204        995          995
  Accrued expenses..........................................     2,450      3,378        3,378
  Accrued royalties.........................................     2,684      4,626        4,626
  Deferred revenues.........................................    15,748     18,022       18,022
                                                              --------   --------     --------
     Total current liabilities..............................    24,196     27,492       27,492
Capital lease obligations...................................       439        233          233
Long-term debt..............................................     5,622      6,232        6,232
                                                              --------   --------     --------
       Total liabilities....................................    30,257     33,957       33,957
                                                              --------   --------     --------
Commitments (Note 13).......................................        --         --           --
Stockholders' deficit:
  Preferred stock, $0.01 par value:
     No shares authorized, issued or outstanding at December
     31, 1997 and 1998; 1,000,000 shares authorized, no
     shares issued and outstanding at December 31, 1998 on a
     pro forma basis (unaudited)............................        --         --           --
  Class P common stock, $0.01 par value:
     500,000 shares authorized, 352,800 and 352,400 shares
     issued and outstanding at December 31, 1997 and 1998,
     respectively, at issuance cost (liquidation preference
     $6,656); no shares authorized, issued and outstanding
     at December 31, 1998 on a pro forma basis
     (unaudited)............................................     3,528      3,524           --
  Common stock, $0.01 par value: 6,500,000, 6,500,000 and
     20,000,000 shares authorized; 3,284,992, 3,329,392,
            shares issued; and 3,234,592, 3,275,392, and
            shares outstanding, at December 31, 1997,
     December 31, 1998 and December 31, 1998 on a pro forma
     basis (unaudited), respectively........................        32         33
  Additional paid-in capital................................       397        759
  Unearned compensation.....................................        --        (39)         (39)
  Accumulated deficit.......................................   (17,432)   (10,444)     (10,444)
  Accumulated other comprehensive loss......................      (132)      (138)        (138)
  Common stock held in treasury, at cost....................        (6)        (6)          (6)
                                                              --------   --------     --------
       Total stockholders' deficit..........................   (13,613)    (6,311)      (6,311)
                                                              --------   --------     --------
       Total liabilities and stockholders' deficit..........  $ 16,644   $ 27,646     $ 27,646
                                                              ========   ========     ========
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.

                                       F-3
<PAGE>   65
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                      CONSOLIDATED STATEMENT OF OPERATIONS
                (IN THOUSANDS, EXCEPT SHARE AND PER SHARE DATA)
 
<TABLE>
<CAPTION>
                                                                YEAR ENDED DECEMBER 31,
                                                        ----------------------------------------
                                                           1996          1997           1998
                                                        ----------    ----------    ------------
<S>                                                     <C>           <C>           <C>
Revenues:
  Web-based product...................................  $       15    $    3,312     $   16,058
  CD Rom product......................................      30,419        27,072         14,370
                                                        ----------    ----------     ----------
                                                            30,434        30,384         30,428
                                                        ----------    ----------     ----------
Cost of revenues:
  Web-based product...................................         295         2,401          7,863
  CD Rom product......................................      12,244        10,444          5,792
                                                        ----------    ----------     ----------
                                                            12,539        12,845         13,655
                                                        ----------    ----------     ----------
  Gross profit........................................      17,895        17,539         16,773
                                                        ----------    ----------     ----------
Operating expenses:
  Selling and marketing...............................       8,572         9,167         11,577
  Platform and product development....................       7,252         6,375          6,313
  General and administrative..........................       3,664         3,401          3,847
                                                        ----------    ----------     ----------
     Total operating expenses.........................      19,488        18,943         21,737
                                                        ----------    ----------     ----------
     Loss from operations.............................      (1,593)       (1,404)        (4,964)
Interest expense......................................        (752)         (943)          (878)
Interest income.......................................          19            13            283
Gain on sale of product line..........................          --           501         12,797
                                                        ----------    ----------     ----------
     Income (loss) before income taxes and
       extraordinary gain.............................      (2,326)       (1,833)         7,238
Provision for income taxes............................          --            --            250
                                                        ----------    ----------     ----------
     Income (loss) before extraordinary gain..........      (2,326)       (1,833)         6,988
Extraordinary gain on early extinguishment of debt....         393            --             --
                                                        ----------    ----------     ----------
     Net income (loss)................................  $   (1,933)   $   (1,833)    $    6,988
Less: income attributable to Class P common stock.....         335           414          1,367
                                                        ----------    ----------     ----------
     Net income (loss) attributable to common stock...  $   (2,268)   $   (2,247)    $    5,621
                                                        ==========    ==========     ==========
Class P common stock:
  Basic and diluted earnings per share................  $     0.95    $     1.17     $     3.88
  Weighted average Class P common shares
     outstanding......................................     353,300       352,800        352,600
Common stock:
  Basic earnings (loss) per share.....................  $    (0.71)   $    (0.70)    $     1.72
  Diluted earnings (loss) per share...................  $    (0.71)   $    (0.70)    $     1.20
  Weighted average common shares outstanding:
     Basic............................................   3,187,695     3,216,385      3,263,309
     Diluted..........................................   3,187,695     3,216,385      4,699,337
Unaudited pro forma earnings per share:
  Basic...............................................                               $
  Diluted.............................................                               $
  Weighted average common shares outstanding:
     Basic............................................
     Diluted..........................................
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
                                       F-4
<PAGE>   66
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
           CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' DEFICIT
                       (IN THOUSANDS, EXCEPT SHARE DATA)
<TABLE>
<CAPTION>
                                     CLASS P
                                   COMMON STOCK        COMMON STOCK      ADDITIONAL
                                 ----------------   ------------------    PAID-IN       UNEARNED     COMPREHENSIVE   ACCUMULATED
                                 SHARES    AMOUNT    SHARES     AMOUNT    CAPITAL     COMPENSATION   INCOME (LOSS)     DEFICIT
                                 -------   ------   ---------   ------   ----------   ------------   -------------   -----------
<S>                              <C>       <C>      <C>         <C>      <C>          <C>            <C>             <C>
Balance, December 31, 1995.....  353,800   $3,538   3,225,600    $32        $376          $ --                        $(13,666)
Comprehensive loss:
 Net loss......................                                                                         $(1,933)        (1,933)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................                                                                            (130)
                                                                                                        -------
     Comprehensive loss........                                                                          (2,063)
                                                                                                        =======
Issuance of common stock
 pursuant to exercise of
 options.......................                        14,976     --           4
Reacquisition and retirement of
 Class P common stock..........   (1,000)    (10)
Reacquisition of common stock
 for treasury..................
                                 -------   ------   ---------    ---        ----          ----                        --------
Balance, December 31, 1996.....  352,800   3,528    3,240,576     32         380            --                         (15,599)
Comprehensive loss:
 Net loss......................                                                                          (1,833)        (1,833)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................                                                                              30
                                                                                                        -------
     Comprehensive loss........                                                                          (1,803)
                                                                                                        =======
Issuance of common stock
 pursuant to exercise of
 options.......................                        44,416     --          17
                                 -------   ------   ---------    ---        ----          ----                        --------
Balance, December 31, 1997.....  352,800   3,528    3,284,992     32         397            --                         (17,432)
Comprehensive income:
 Net income....................                                                                           6,988          6,988
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................                                                                              (6)
                                                                                                        -------
     Comprehensive income......                                                                         $ 6,982
                                                                                                        =======
Issuance of common stock
 pursuant to exercise of
 options.......................                        44,400      1          22
Unearned compensation relating
 to grants of stock options....                                               45           (45)
Compensation relating to grants
 of stock options..............                                                              6
Compensation relating to
 modification of stock options
 on sale of product line.......                                              295
Reacquisition and retirement of
 Class P common stock..........     (400)     (4)
Reacquisition of common stock
 for treasury..................
                                 -------   ------   ---------    ---        ----          ----                        --------
Balance, December 31, 1998.....  352,400   $3,524   3,329,392    $33        $759          $(39)                       $(10,444)
                                 =======   ======   =========    ===        ====          ====                        ========
 
<CAPTION>
                                  ACCUMULATED
                                     OTHER       TREASURY STOCK        TOTAL
                                 COMPREHENSIVE   ---------------   STOCKHOLDERS'
                                     LOSS        SHARES   AMOUNT      DEFICIT
                                 -------------   ------   ------   -------------
<S>                              <C>             <C>      <C>      <C>
Balance, December 31, 1995.....      $ (32)      41,400    $(5)      $ (9,757)
Comprehensive loss:
 Net loss......................                                        (1,933)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................       (130)                              (130)
     Comprehensive loss........
Issuance of common stock
 pursuant to exercise of
 options.......................                                             4
Reacquisition and retirement of
 Class P common stock..........                                           (10)
Reacquisition of common stock
 for treasury..................                   9,000     (1)            (1)
                                     -----       ------    ---       --------
Balance, December 31, 1996.....       (162)      50,400     (6)       (11,827)
Comprehensive loss:
 Net loss......................                                        (1,833)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................         30                                 30
     Comprehensive loss........
Issuance of common stock
 pursuant to exercise of
 options.......................                                            17
                                     -----       ------    ---       --------
Balance, December 31, 1997.....       (132)      50,400     (6)       (13,613)
Comprehensive income:
 Net income....................                                         6,988
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................         (6)                                (6)
     Comprehensive income......
Issuance of common stock
 pursuant to exercise of
 options.......................                                            23
Unearned compensation relating
 to grants of stock options....                                            --
Compensation relating to grants
 of stock options..............                                             6
Compensation relating to
 modification of stock options
 on sale of product line.......                                           295
Reacquisition and retirement of
 Class P common stock..........                                            (4)
Reacquisition of common stock
 for treasury..................                   3,600     --             --
                                     -----       ------    ---       --------
Balance, December 31, 1998.....      $(138)      54,000    $(6)      $ (6,311)
                                     =====       ======    ===       ========
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
 
                                       F-5
<PAGE>   67
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                      CONSOLIDATED STATEMENT OF CASH FLOWS
                                 (IN THOUSANDS)
 
<TABLE>
<CAPTION>
                                                                 YEAR ENDED DECEMBER 31,
                                                              ------------------------------
                                                               1996       1997        1998
                                                              -------    -------    --------
<S>                                                           <C>        <C>        <C>
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS
Cash flows relating to operating activities
  Net income (loss).........................................  $(1,933)   $(1,833)   $  6,988
  Adjustments to reconcile net income (loss) to net cash
    provided (used) by operating activities:
    Depreciation and amortization...........................    2,670      1,776       1,518
    Compensation expense relating to grants of stock
       options..............................................       --         --           6
    Amortization of debt discount...........................      108        142         121
    Loss on sale leaseback transaction......................       --         --          45
    Gain on sale of product line............................       --       (501)    (12,797)
    Gain on early extinguishment of debt....................     (393)        --          --
    Changes in assets and liabilities:
       Accounts receivable..................................     (781)        17        (946)
       Deferred subscription costs..........................     (178)      (748)     (2,217)
       Prepaid expenses and other assets....................     (255)        14         (43)
       Accounts payable.....................................      509       (459)       (213)
       Accrued expenses.....................................      507        758       1,075
       Accrued royalties....................................       76       (128)      2,283
       Deferred revenues....................................      943        453       5,373
                                                              -------    -------    --------
    Net cash provided (used) by operating activities........    1,273       (509)      1,193
                                                              -------    -------    --------
Cash flows relating to investing activities
  Investment in certificate of deposit......................       --         --        (100)
  Purchases of property and equipment.......................   (1,332)      (878)     (1,252)
  Capitalization of software development costs..............     (300)       (75)       (200)
  Net proceeds from sale of product line....................       --        501      10,563
                                                              -------    -------    --------
    Net cash provided (used) by investing activities........   (1,632)      (452)      9,011
                                                              -------    -------    --------
Cash flows relating to financing activities
  Proceeds from issuance of common stock....................        4         17          23
  Repurchase of Class P common stock and common stock.......      (11)        --          (4)
  Net borrowings (repayments) under line of credit..........     (400)       883      (1,183)
  Borrowings under term loan................................      575         --          --
  Repayments of term loan...................................     (208)      (228)       (347)
  Proceeds from sale and leaseback of fixed assets..........      289        753         228
  Repayments of capital lease obligations...................     (402)      (607)       (684)
                                                              -------    -------    --------
    Net cash provided (used) by financing activities........     (153)       818      (1,967)
                                                              -------    -------    --------
Effect of exchange rate changes on cash and cash
  equivalents...............................................       81        (51)         87
                                                              -------    -------    --------
Increase (decrease) in cash and cash equivalents............     (431)      (194)      8,324
Cash and cash equivalents, beginning of year................      966        535         341
                                                              -------    -------    --------
Cash and cash equivalents, end of year......................  $   535    $   341    $  8,665
                                                              =======    =======    ========
Supplemental disclosure of cash flow information:
  Cash paid for interest....................................  $   218    $   301    $    209
  Cash paid for taxes.......................................       --         --         175
Supplemental disclosure of noncash investing and financing
  activities:
  Additions to capital lease obligations for purchases of
    fixed assets............................................  $   430    $    87    $    183
  Additions to capital lease obligations for sale and
    leaseback of fixed assets...............................      289        753         228
  Additions to long-term debt for accrued interest..........      440        480         489
  Exchange of property and equipment for the retirement of
    capital lease obligations...............................       --         --          41
</TABLE>
 
  The accompanying notes are an integral part of these consolidated financial
                                  statements.
                                       F-6
<PAGE>   68
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
 
1.  NATURE OF BUSINESS
 
     OneSource Information Services, Inc. and its wholly-owned subsidiary
provide Web-based business and financial information to professionals in
corporations and other enterprises. OneSource primarily sells its products
through a direct sales force located throughout the United States and United
Kingdom. OneSource manages its business as a single segment.
 
2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
PRINCIPLES OF CONSOLIDATION
 
     The consolidated financial statements include the accounts of OneSource
Information Services, Inc. and OneSource Information Services Limited, its
wholly-owned subsidiary (collectively, "OneSource"). All significant
intercompany transactions and balances have been eliminated.
 
REVENUE RECOGNITION
 
     OneSource's products are sold on a subscription basis pursuant to customer
contracts that span varying periods of time but are generally for a period of
one year. In accordance with its customer agreements, OneSource initially
records receivables and defers the related revenue at the time amounts are
billed to customers. Revenues are recognized ratably over the related
subscription period.
 
SUBSCRIPTION COSTS
 
     Subscription costs represent sales commission and royalty costs that are
directly associated with securing a subscription and procuring information to be
delivered over the subscription period, respectively. These costs are deferred
and amortized ratably over the associated subscription period as a component of
selling and marketing expense and cost of revenues, respectively. At December
31, 1997 and 1998, deferred subscription costs consisted of $1,365,000 and
$1,250,000, respectively, related to sales commissions and $3,672,000 and
$5,412,000, respectively, related to royalties.
 
CASH AND CASH EQUIVALENTS
 
     Cash equivalents consist of money market funds with original maturities of
three months or less and are stated at cost which approximates fair market
value. These funds are managed by a financial institution with a strong credit
rating. Accordingly, the investments are subject to minimal credit and market
risks.
 
PROPERTY AND EQUIPMENT
 
     Property and equipment are recorded at cost and depreciated over their
estimated useful lives, generally three to five years, using the straight-line
method. Equipment held under capital leases is stated at the fair value of the
equipment at inception of the leases and is amortized on a straight-line basis
over the term of the leases.
 
                                       F-7
<PAGE>   69
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
PLATFORM AND PRODUCT DEVELOPMENT AND SOFTWARE DEVELOPMENT COSTS
 
     Platform and product development costs, other than certain software
development costs, are charged to expense as incurred. Software development
costs incurred subsequent to the establishment of technological feasibility, and
prior to general release of the product, are capitalized and amortized on a
straight-line basis over the estimated useful lives of the related products,
generally twenty-four to thirty-six months. For the years ended December 31,
1996, 1997 and 1998, amortization of capitalized software development costs
amounted to $340,000, $413,000 and $198,000, respectively.
 
FINANCIAL INSTRUMENTS
 
     Fair values of OneSource's financial instruments, which include cash and
cash equivalents, restricted time deposits, accounts receivable, long-term debt
and capital lease obligations are based on quoted market prices and assumptions
concerning the amount and timing of estimated future cash flows and assumed
discount rates reflecting varying degrees of perceived risk. The carrying value
of these financial instruments approximated their fair value at December 31,
1997 and 1998.
 
CONCENTRATION OF CREDIT RISK
 
     Concentration of credit risk with respect to accounts receivable is limited
due to the large number of companies comprising OneSource's client base. Ongoing
credit evaluations of customers' financial condition are performed and
collateral is generally not required. OneSource maintains reserves for potential
credit losses and such losses, in the aggregate, have not exceeded management's
expectations.
 
ACCOUNTING FOR STOCK-BASED COMPENSATION
 
     OneSource accounts for stock-based compensation to employees in accordance
with Accounting Principles Board Opinion ("APB") No. 25, "Accounting for Stock
Issued to Employees" and related interpretation. Accordingly, compensation
expense is recorded for options issued to employees in fixed amounts to the
extent that the fixed exercise prices are less than the fair market value of
OneSource's common stock at the date of grant. OneSource follows the disclosure
requirements of Statement of Financial Accounting Standards ("SFAS") No. 123,
"Accounting for Stock-Based Compensation" (Note 8). All stock-based awards to
non-employees are accounted for at their fair value in accordance with SFAS No.
123.
 
UNAUDITED PRO FORMA BALANCE SHEET
 
     Prior to the closing of OneSource's initial public offering, each
outstanding share of Class P common stock (the "Class P stock") will be
reclassified into one share of common stock plus an additional number of shares
of common stock (determined by dividing the preference amount for such share by
the assumed initial public offering price of $      per share). In addition,
upon the closing of OneSource's initial public offering, OneSource will file a
Restated Certificate of Incorporation which will authorize 1,000,000 shares of a
single class of undesignated preferred
 
                                       F-8
<PAGE>   70
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
stock, $0.01 par value per share, will cancel authorization of the Class P
common stock and will have authorized 20,000,000 shares of common stock. This
reclassification and other changes have been reflected in the unaudited pro
forma balance sheet as of December 31, 1998.
 
EARNINGS PER SHARE AND UNAUDITED PRO FORMA EARNINGS PER SHARE
 
     Earnings per share is computed in accordance with SFAS No. 128, "Earnings
Per Share." SFAS No. 128 requires the presentation of two amounts, basic
earnings per share and diluted earnings per share. The two-class method of
computing earnings per share has been used since the Class P stock and the
common stock share ratably in earnings remaining subsequent to the 12% yield on
the Class P stock.
 
     Earnings per share of Class P stock is calculated by dividing the yield
earned and income (loss) attributable to Class P stock by the weighted average
number of shares of Class P stock outstanding during the period. Diluted
earnings per share is the same for all periods presented as there are no
securities outstanding that would result in dilution for Class P stock.
 
     Earnings per share of common stock is calculated by dividing income (loss)
attributable to common stock by the weighted average number of shares of common
stock outstanding during the period. Diluted earnings per share is calculated by
considering the impact of potential common stock as if they were converted into
common stock at the beginning of the period. Potential common stock equivalents
are not included in loss periods as they are anti-dilutive.
 
     Unaudited pro forma basic and diluted earnings per share of common stock
for the year ended December 31, 1998 have been calculated based on net income
applicable to all classes of common stock and assuming the reclassification of
OneSource's Class P common stock prior to the completion of this offering, as if
such reclassification had occurred at January 1, 1998. Each share of Class P
common stock will be reclassified into one share of common stock plus an
additional number of shares of common stock (determined by dividing the
preference amount for such share by the assumed initial public offering price of
$     per share).
 
FOREIGN CURRENCY TRANSLATION
 
     Assets and liabilities of OneSource's United Kingdom operations, where the
local currency is the functional currency, are translated into US dollars at the
exchange rate in effect as of the balance sheet date, while revenues and
expenses are translated at average exchange rates during the period. The
resultant translation adjustment is reflected as a separate component of
stockholders' deficit. Transaction gains and losses, which are not material in
amount, are reflected in the consolidated statement of operations.
 
USE OF ESTIMATES
 
     The preparation of financial statements in conformity with generally
accepted accounting principles requires OneSource management to make estimates
and assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the financial
statements and the reported amounts of revenues and expenses during the
reporting period. Actual results could differ from those estimates.

                                       F-9
<PAGE>   71
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS
 
     In March 1998, the Accounting Standards Executive Committee ("AcSEC")
issued Statement of Position ("SOP") 98-1, "Accounting for the Costs of Computer
Software Developed or Obtained for Internal Use." SOP 98-1 establishes the
accounting for costs of software products developed or purchased for internal
use, including when such costs should be capitalized. OneSource does not expect
SOP 98-1, which is effective for OneSource beginning January 1, 1999, to have a
material effect on OneSource's financial condition or results of operations.
 
     In April 1998, the AcSEC issued SOP 98-5, "Reporting on the Costs of
Start-Up Activities." Start-up activities are defined broadly as those one-time
activities relating to opening a new facility, introducing a new product or
service, conducting business in a new territory, conducting business with a new
class of customer, commencing some new operation or organizing a new entity.
Under SOP 98-5, the cost of start-up activities should be expensed as incurred.
SOP 98-5 is effective for OneSource's calendar year 1999 financial statements
and OneSource does not expect its adoption to have a material effect on
OneSource's financial condition or results of operations.
 
     In June 1998, the Financial Accounting Standards Board issued SFAS No. 133,
"Accounting for Derivative Instruments and Hedging Activities." The new standard
establishes accounting and reporting standards for derivative instruments,
including certain derivative instruments embedded in other contracts, and for
hedging activities. SFAS No. 133 is effective for all fiscal quarters of fiscal
years beginning after June 15, 1999. OneSource does not expect SFAS No. 133 to
have a material effect on its financial condition or results of operations.
 
3.  PROPERTY AND EQUIPMENT
 
     Property and equipment consists of the following:
 
<TABLE>
<CAPTION>
                                                     DECEMBER 31,
                                                  ------------------
                                                   1997       1998
                                                  -------    -------
                                                    (IN THOUSANDS)
<S>                                               <C>        <C>
Office and computer equipment...................  $ 5,222    $ 5,478
Furniture and fixtures..........................      293        326
                                                  -------    -------
                                                    5,515      5,804
Less: accumulated depreciation and
  amortization..................................   (3,689)    (4,034)
                                                  -------    -------
                                                  $ 1,826    $ 1,770
                                                  =======    =======
</TABLE>
 
     At December 31, 1997 and 1998, office and computer equipment under capital
leases totaled $2,112,000 and $1,304,000, respectively. Related accumulated
amortization of assets under capital leases totaled $1,158,000 and $702,000 at
December 31, 1997 and 1998, respectively. During the years ended December 31,
1996, 1997 and 1998, OneSource sold and leased back certain computer equipment
with net book values of $308,000, $788,000, and
 
                                      F-10
<PAGE>   72
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
$237,000, respectively for cash proceeds of $289,000, $753,000 and $228,000.
During 1998, OneSource retired $525,000 of fully depreciated property and
equipment.
 
4.  BORROWINGS
 
NOTES PAYABLE
 
     OneSource entered into a credit agreement (the "Agreement") with a bank, as
amended, which provides for a line of credit (the "Line") of up to $2,500,000
through April 1, 1998 and a term loan (the "Term Loan") of $750,000 to be used
for financing equipment purchases. At December 31, 1997, borrowings under the
Line were $1,183,000 and borrowings under the Term Loan were $347,000. During
1998, the Line and the Term Loan expired and were repaid in full.
 
LONG-TERM DEBT
 
     In connection with the acquisition of the business in 1993, OneSource
entered into a subordinated note agreement with the seller with a face amount of
$5,000,000 (the "Note"). The Note bears interest at 8% per annum, payable
annually commencing March 31, 1995 and has been discounted to reflect the market
rate of 12% at the time of issuance. The initial discount totaling $938,000 is
being amortized to interest expense over the life of the Note using the
effective interest method. As of December 31, 1998, the unamortized discount was
$291,000. Interest payments may be added to the unpaid principal of the Note if
OneSource's cash flow, as defined in the Note agreement, is less than a
specified amount.
 
     The Note, and any accrued but unpaid interest thereon, is due on the
earlier of i) September 8, 2000, ii) the date OneSource's stockholders, in
connection with an acquisition, cease to own a majority of the capital stock of
OneSource, or iii) the date OneSource sells substantially all of its assets. In
the event OneSource issues equity securities with net proceeds to OneSource in
excess of $10,000,000, OneSource is required to make a prepayment of the
principal amount as defined in the Note agreement. The Note agreement requires
OneSource to comply with certain restrictive covenants, including the
maintenance of specified financial ratios, and restricts OneSource from paying
dividends.
 
     In December 1996, OneSource reached a settlement agreement for an alleged
breach by the seller of a provision of the Note agreement regarding the initial
acquisition of the business. Under the terms of the settlement, the seller
forgave $393,000, or $0.11 per common share, of the principal on the Note, which
amount has been recognized as an extraordinary gain on early extinguishment of
debt.
 
     As of December 31, 1998, the carrying value of the Note was $6,232,000. In
accordance with the terms of the Note agreement, OneSource has added $1,523,000
to the principal of the Note for interest which had accrued through the end of
December 31, 1997. Accrued interest related to the Note was $504,000 for the
year ended December 31, 1998 and, since OneSource met the cash flow requirements
set forth in the Note agreement, such amount is due by March 31, 1999.
 
                                      F-11
<PAGE>   73
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
5.  EARNINGS PER SHARE
 
     The following tables set forth the computation of earnings per share of
common stock and Class P stock from net income (loss):
 
<TABLE>
<CAPTION>
                                                 YEAR ENDED DECEMBER 31,
                                           -----------------------------------
                                             1996         1997         1998
                                           ---------    ---------    ---------
<S>                                        <C>          <C>          <C>
Numerator for common stock (in
  thousands):
  Net income (loss)......................  $  (1,933)   $  (1,833)   $   6,988
  Less: income attributable to Class P
     stock...............................        335          414        1,367
                                           ---------    ---------    ---------
                                           $  (2,268)   $  (2,247)   $   5,621
                                           =========    =========    =========
Denominator for common stock:
  Weighted average shares outstanding
     used for basic earnings per share...  3,187,695    3,216,385    3,263,309
Effect of dilutive securities:
  Stock options..........................         --           --    1,195,624
  Common stock warrants..................         --           --      240,404
                                           ---------    ---------    ---------
  Weighted average shares outstanding
     used for diluted earnings per
     share...............................  3,187,695    3,216,385    4,699,337
                                           =========    =========    =========
</TABLE>
 
     Total potential common equivalent shares consist of 1,743,448 stock options
outstanding with a weighted average exercise price of $2.91 per share and
240,404 common stock warrants exercisable at $0.12 per share as of December 31,
1998.
 
<TABLE>
<CAPTION>
                                                 YEAR ENDED DECEMBER 31,
                                           -----------------------------------
                                             1996         1997         1998
                                           ---------    ---------    ---------
                                                     (IN THOUSANDS)
<S>                                        <C>          <C>          <C>
Numerator for Class P stock:
  Yield earned by Class P stock..........  $     586    $     660    $     742
  Income (loss) attributable to Class P
     stock...............................       (251)        (246)         625
                                           ---------    ---------    ---------
                                           $     335    $     414    $   1,367
                                           =========    =========    =========
</TABLE>
 
     Basic and diluted earnings per share of Class P stock are the same for all
periods presented since there are no potentially dilutive securities.
 
6.  CLASS P COMMON STOCK AND COMMON STOCK
 
     In connection with its initial capitalization, OneSource issued 356,400
shares of Class P stock and 3,207,600 shares of common stock at $10.00 per share
and $0.12 per share, respectively. The holders of the Class P stock, as a
separate class, are entitled to receive first all or a portion of any
distribution, as defined, until the "preference amount" and the original
 
                                      F-12
<PAGE>   74
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
issuance cost has been paid in full. The preference amount is 12% compounded
quarterly. After all such payments have been made, the holders of the Class P
stock and of the common stock shall share pro rata in the remaining portion of
the distribution, as a single class. As of December 31, 1998, no dividends on
either the Class P stock or the common stock have been declared or paid, and no
payments of the aggregate yield have been made to the Class P stockholders. As a
result, the Class P stock is stated at its original issuance cost of $10.00 per
share. As of December 31, 1998, the liquidation preference of these shares was
$6,656,000.
 
     All holders of Class P stock and all holders of common stock are entitled
to one vote per share on all matters to be voted upon by OneSource's
stockholders. The Class P stock is not convertible into common stock without the
prior agreement of the Class P stockholders and OneSource.
 
7.  WARRANTS
 
     In connection with the Note agreement (Note 4), OneSource issued a warrant
exercisable at $0.12 per share for 200,000 shares of OneSource's common stock.
The warrant is currently exercisable and expires on September 8, 2002. In
connection with the credit agreement (Note 4), OneSource also issued a warrant
to the Term Loan holder which entitles the holder to purchase 40,404 shares of
OneSource's common stock at $0.12 per share. The warrant is currently
exercisable and expires on the later of September 8, 2003 or five years from the
effective date of an initial public offering of OneSource's common stock. The
fair value of these warrants at the date of issuance was determined to be
$10,000 in the aggregate. OneSource has reserved 240,404 shares of common stock
for issuance upon exercise of the above warrants.
 
8.  STOCK PLANS
 
     The 1993 Stock Purchase and Option Plan (the "1993 Plan") provides for the
grant of incentive stock options and non-qualified stock options for the
purchase of up to an aggregate of 2,100,000 shares of OneSource's common stock
by employees, directors, consultants and advisors of OneSource. The Board of
Directors determines the term of each option, option price, number of shares for
which each option is granted, whether restrictions will be imposed on the shares
subject to options, and the vesting schedule of each option. The exercise price
for incentive stock options granted may not be less than the fair value per
share of the underlying common stock on the date granted as determined by the
Board of Directors (not less than 110% of the fair value for options granted to
holders of more than 10% of the voting stock of OneSource). Additionally, the
term of the options cannot exceed ten years (five years for options granted to
holders of more than 10% of the voting stock of OneSource). The options
generally vest over a four-year period.
 
     In February 1999, the Board of Directors of OneSource approved the 1999
Stock Option and Incentive Plan (the "1999 Stock Option Plan") to be effective
upon the closing of OneSource's initial public offering. The 1999 Stock Option
Plan provides for the grant of stock-based awards to employees, officers and
directors of, and consultants or advisors to,
 
                                      F-13
<PAGE>   75
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
OneSource. A total of 800,000 shares of common stock are authorized for issuance
upon the exercise of options or other awards granted under the 1999 Stock Option
Plan.
 
     In February 1999, the Board of Directors of OneSource approved the 1999
Employee Stock Purchase Plan (the "1999 Purchase Plan"), to be effective upon
the closing of OneSource's initial public offering. The 1999 Purchase Plan
provides for the issuance of a maximum of 100,000 shares of common stock.
 
     Transactions under the 1993 Plan during the years ended December 31, 1996,
1997 and 1998 are summarized as follows:
 
<TABLE>
<CAPTION>
                                                              WEIGHTED-
                                               NUMBER OF       AVERAGE
                                                SHARES      EXERCISE PRICE
                                               ---------    --------------
<S>                                            <C>          <C>
Outstanding--December 31, 1995...............  1,382,756        $2.17
  Granted (weighted average fair value of
     $0.25)..................................    620,700         3.53
  Exercised..................................    (14,976)        0.25
  Forfeited..................................    (85,876)        1.39
                                               ---------
Outstanding--December 31, 1996...............  1,902,604         2.67
  Granted (weighted average fair value of
     $0.25)..................................    144,600         3.52
  Exercised..................................    (44,416)        0.39
  Forfeited..................................   (230,540)        2.99
                                               ---------
Outstanding--December 31, 1997...............  1,772,248         2.75
  Granted (weighted average fair value of
     $1.66)..................................    100,700         4.44
  Exercised..................................    (44,400)        0.55
  Forfeited..................................    (85,100)        2.73
                                               ---------
Outstanding--December 31, 1998...............  1,743,448         2.91
                                               =========
</TABLE>
 
     The following table summarizes information about stock options outstanding
at December 31, 1998:
 
<TABLE>
<CAPTION>
                                                    WEIGHTED-
                                                     AVERAGE
                                                    REMAINING       NUMBER OF
                                      NUMBER       CONTRACTUAL       OPTIONS
EXERCISE PRICE                      OF OPTIONS    LIFE IN YEARS    EXERCISABLE
--------------                      ----------    -------------    -----------
<S>                                 <C>           <C>              <C>
$0.25.............................    370,548          4.9            365,973
 2.78.............................    675,900          6.4            496,950
 4.45.............................    697,000          6.7            478,825
                                    ---------                       ---------
                                    1,743,448          6.2          1,341,748
                                    =========                       =========
</TABLE>
 
                                      F-14
<PAGE>   76
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     As of December 31, 1996 and 1997, 925,853 and 1,214,860 options were
exercisable, respectively, under the 1993 Plan. As of December 31, 1998, there
were 252,760 shares of common stock available for grant to employees under the
1993 Plan.
 
     The fair value of each option grant is estimated on the date of grant using
the minimum value method with the following assumptions for grants in 1996, 1997
and 1998: dividend yield of 0.0% for all years; risk-free interest rates of
6.4%, 6.2% and 5.2% for 1996, 1997 and 1998, respectively; and a
weighted-average expected option term of 5 years for all years.
 
     Compensation expense has been recognized for OneSource's stock option plan
under APB No. 25. Had compensation cost been determined based on the fair value
of the options at the grant date consistent with the provisions of SFAS No. 123,
OneSource's net income (loss) and earnings (loss) per share would have been
increased to the pro forma amounts indicated below:
 
<TABLE>
<CAPTION>
                                                   YEAR ENDED DECEMBER 31,
                                                 ----------------------------
                                                  1996       1997       1998
                                                 -------    -------    ------
<S>                                              <C>        <C>        <C>
Net income (loss) (in thousands):
  As reported..................................  $(1,933)   $(1,833)   $6,988
  Pro-forma....................................   (2,006)    (1,890)    6,909
Basic and diluted earnings per Class P common
  share:
  As reported..................................     0.95       1.17      3.88
  Pro-forma....................................     0.92       1.15      3.85
Basic earnings per common share:
  As reported..................................    (0.71)     (0.70)     1.72
  Pro-forma....................................    (0.73)     (0.71)     1.70
Diluted earnings per common share:
  As reported..................................    (0.71)     (0.70)     1.20
  Pro-forma....................................    (0.73)     (0.71)     1.18
</TABLE>
 
     Because options vest over several years and additional option grants are
expected to be made in future years, results of operations for future years may
be materially different if the provisions of SFAS No. 123 are applied.
 
     In conjunction with the sale of the CD-Insurance division, OneSource
modified the terms of 111,352 stock options held by terminated employees. In
accordance with APB No. 25, compensation expense of $295,000 was recorded as a
reduction of the gain on the sale of the insurance division in the year ended
December 31, 1998.
 
     During 1998, 99,800 stock options were granted with an exercise price of
$4.45 per share and 900 stock options were granted with an exercise price of
$2.78 per share; these exercise prices were below the estimated fair market
value of the common stock at the date of grant. Unearned compensation of $45,000
was recorded, in accordance with APB No. 25, and will be amortized over the
related vesting period. Compensation expense of $6,000 was recorded in the
 
                                      F-15
<PAGE>   77
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
year ended December 31, 1998. Options issued during 1996 and 1997 were granted
with exercise prices above the estimated fair market value of the common stock
at the date of grant.
 
9.  INCOME TAXES
 
     Components of the income (loss) before income taxes and extraordinary gain
and of the current provision for income taxes are as follows:
 
<TABLE>
<CAPTION>
                                                   YEAR ENDED DECEMBER 31,
                                                 ----------------------------
                                                  1996       1997       1998
                                                 -------    -------    ------
                                                        (IN THOUSANDS)
<S>                                              <C>        <C>        <C>
Income (loss) before income taxes and
  extraordinary gain:
  Domestic.....................................  $(1,976)   $(2,124)   $7,204
  Foreign......................................     (350)       291        34
                                                 -------    -------    ------
                                                 $(2,326)   $(1,833)   $7,238
                                                 =======    =======    ======
Current provision for income taxes:
  Federal......................................  $    --    $    --    $  200
  State........................................       --         --        45
  Foreign......................................       --         --         5
                                                 -------    -------    ------
                                                 $    --    $    --    $  250
                                                 =======    =======    ======
</TABLE>
 
     OneSource had no deferred provision for income taxes in each of the years
ended December 31, 1996, 1997 and 1998 due to the offsetting effects of the
valuation allowance on its net deferred tax assets. There was no income tax
effect related to the extraordinary gain on early extinguishment of debt in
1996. Provision has not been made for US or additional foreign taxes on
undistributed earnings of foreign subsidiaries as those earnings have been
permanently reinvested. Such taxes, if any, are not expected to be significant.
 
                                      F-16
<PAGE>   78
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     Income taxes computed using the federal statutory income tax rate differ
from OneSource's effective tax rate primarily due to the following:
 
<TABLE>
<CAPTION>
                                                    YEAR ENDED DECEMBER 31,
                                                   -------------------------
                                                   1996     1997      1998
                                                   -----    -----    -------
                                                        (IN THOUSANDS)
<S>                                                <C>      <C>      <C>
Income tax expense (benefit) at US federal
  statutory tax rate.............................  $(657)   $(623)   $ 2,461
State income taxes, net of federal tax effect....   (115)    (125)       508
Permanent items..................................     79       20         21
Other............................................     20       (4)        36
Change in deferred tax asset valuation
  allowance......................................    673      732     (2,776)
                                                   -----    -----    -------
Provision for income taxes.......................  $  --    $  --    $   250
                                                   =====    =====    =======
</TABLE>
 
     Components of OneSource's deferred tax assets and liabilities are as
follows:
 
<TABLE>
<CAPTION>
                                                     DECEMBER 31,
                                                  ------------------
                                                   1997       1998
                                                  -------    -------
                                                    (IN THOUSANDS)
<S>                                               <C>        <C>
Deferred tax assets:
  Net operating loss carryforwards..............  $ 3,394    $   238
  Depreciation..................................      378        537
  Accrued expenses..............................      222        623
  Deferred revenues.............................    2,159      1,342
  Equity compensation...........................       --        123
  Miscellaneous.................................      120        133
                                                  -------    -------
     Gross deferred tax asset...................    6,273      2,996
  Less: valuation allowance.....................   (4,544)    (1,768)
                                                  -------    -------
     Total deferred tax assets..................    1,729      1,228
                                                  -------    -------
Deferred tax liabilities:
  Prepaid expenses..............................    1,068        513
  Deferred royalties............................      253        252
  Amortization of debt discount.................      163        217
  Capitalized software development costs........      126        127
  Tax operating leases..........................      119        119
                                                  -------    -------
     Total deferred tax liabilities.............    1,729      1,228
                                                  -------    -------
Net deferred tax assets.........................  $    --    $    --
                                                  =======    =======
</TABLE>
 
                                      F-17
<PAGE>   79
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     Realization of OneSource's net deferred tax assets is contingent upon the
generation of future taxable income. Due to the uncertainty of realization of
these tax benefits, OneSource has provided a valuation allowance for the full
amount of its net deferred tax assets.
 
     During 1998, OneSource utilized $8,000,000 of net operating loss
carryforwards. At December 31, 1998, OneSource had net operating loss
carryforwards of $575,000 for foreign tax purposes which do not expire. Under
the provisions of the Internal Revenue Code, if certain substantial changes in
OneSource's ownership should occur, the amount of net operating loss
carryforwards which could be utilized annually to offset future taxable income
and income tax liability may be limited. The amount of any annual limitation is
determined based upon OneSource's value prior to an ownership change.
 
10.  SALE OF PRODUCT LINES
 
     In June 1997, OneSource sold its CD Rom banking product line for $650,000
in cash. In connection with the sale, OneSource entered a non-compete agreement
for five years. As a result of the sale, OneSource recorded a gain of $501,000
which is net of expenses of $149,000 incurred in conjunction with the sale. No
assets or liabilities with recorded net book values were transferred in
connection with this product line sale.
 
     In May 1998, OneSource sold its CD-Insurance division for $11,000,000 in
cash and entered a software license agreement for $4,000,000 to be received in
equal quarterly installments for two years commencing January 1, 1999. In
connection with the sale, OneSource also entered a non-compete agreement for
five years. As a result of the sale, OneSource recorded a gain of $12,797,000
which includes: (i) the recognition of $3,124,000 of deferred revenues and
$595,000 of deferred subscription costs based upon the assumption by the buyer
of all obligations to service the existing subscriber base of the insurance
division, (ii) $530,000 of employee severance costs and (iii) $202,000 of
expenses associated with the sale. Payments pertaining to the software license
agreement will be recognized in other income as support services are performed
and payments become due in accordance with the agreement.
 
11.  EMPLOYEE BENEFIT PLANS
 
     After three months of service, OneSource employees are eligible to
participate in a tax deferred savings plan (the "Savings Plan") under Section
401(k) of the Internal Revenue Code. OneSource matches 25% of the first 6%
contributed by the employee, and the employee becomes fully vested in
OneSource's matching contribution after three years of service. OneSource's
contributions to the Savings Plan totaled $122,000, $116,000 and $120,000 for
the years ended December 31, 1996, 1997 and 1998, respectively.
 
12.  RELATED PARTY TRANSACTIONS
 
     At December 31, 1997 and 1998, OneSource had accounts receivable of
$117,000 and $335,000, respectively, due from two stockholders. OneSource
recognized revenue of $200,000, $292,000 and $318,000 in the years ended
December 31, 1996, 1997, and 1998 respectively, from these parties.
 
                                      F-18
<PAGE>   80
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     Management fees paid to a stockholder and an affiliate of another
stockholder totaling $200,000 for each of the years ended December 31, 1996,
1997 and 1998 are included in general and administrative expenses.
 
13.  COMMITMENTS
 
  Leases
 
     OneSource leases facilities and certain equipment under various
noncancellable operating lease agreements. Total rent expense under such leases
was $1,271,000, $1,191,000 and $1,146,000 for the years ended December 31, 1996,
1997, and 1998, respectively. Future minimum lease commitments under all
noncancellable capital and operating leases at December 31, 1998 are as follows:
 
<TABLE>
<CAPTION>
                                                     CAPITAL    OPERATING
                                                     LEASES      LEASES
                                                     -------    ---------
                                                        (IN THOUSANDS)
<S>                                                  <C>        <C>
1999...............................................   $490       $  920
2000...............................................    207          231
2001...............................................     80          223
2002...............................................     --          221
2003...............................................     --           68
                                                      ----       ------
Total minimum lease payments.......................    777       $1,663
                                                                 ======
Less: amount representing interest.................     73
                                                      ----
Present value of net minimum lease payments,
  including current maturities of $471.............   $704
                                                      ====
</TABLE>
 
     In January 1999, OneSource entered into a five-year noncancellable
operating lease for a new operating facility. Minimum yearly rental payments
will be $655,000, commencing in June 1999. Pursuant to the lease, OneSource
entered into a $415,000 irrevocable letter of credit collateralized by a
certificate of deposit.
 
  Restricted Time Deposit
 
     In connection with a facility lease, OneSource is required to maintain, on
behalf of the landlord, an irrevocable letter of credit with a bank in the
amount of $100,000 over the term of the lease. In addition, OneSource was
required to maintain a certificate of deposit in an equal amount as security for
the letter of credit.
 
                                      F-19
<PAGE>   81
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
14.  GEOGRAPHIC INFORMATION
 
     Revenue was distributed geographically as follows:
 
<TABLE>
<CAPTION>
                                           YEAR ENDED DECEMBER 31,
                                        -----------------------------
                                         1996       1997       1998
                                        -------    -------    -------
                                               (IN THOUSANDS)
<S>                                     <C>        <C>        <C>
United States.........................  $25,294    $24,193    $23,428
United Kingdom........................    5,140      6,191      7,000
                                        -------    -------    -------
                                        $30,434    $30,384    $30,428
                                        =======    =======    =======
</TABLE>
 
     Substantially all of OneSource's identifiable assets are located in the
United States.
 
                                      F-20
<PAGE>   82
 
     [The graphic contains the OneSource logo in the center of the page. Reading
from the top right diagonally to the bottom left of the page is the following
text: Turning World Class Information into Integrated Solutions For Demanding
Business Professionals Worldwide. The top left of the page depicts the names and
logos of the following OneSource information providers: The Investext Group;
Market Guide; Standard & Poor's; Comtex; Financial Times; Corp Tech; WorldScope
Disclosure; Hoover's Inc.; Reuters; and Dun & Bradstreet. The bottom half of the
page depicts the following OneSource customers by name and logo displayed
according to the following industry sectors noted in the text:
 
  Financial Institutions:
 
     Credit Suisse; Merrill Lynch; American Express: Bank of America.
 
  Professional Services:
 
     Bain & Company; KMPG; Deloitte Touche Tohmatsu; Ernst & Young.
 
  High Tech:
 
     Oracle; SAP; Platinum; IBM.
 
  Leading Corporations:
 
     Boeing; MCI Worldcom; BT; Nortel Networks.]
<PAGE>   83
 
------------------------------------------------------
------------------------------------------------------
 
     YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS. WE
HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION DIFFERENT FROM THAT
WHICH IS SET FORTH IN THIS PROSPECTUS. WE ARE OFFERING TO SELL SHARES OF COMMON
STOCK AND SEEKING OFFERS TO BUY SHARES OF COMMON STOCK ONLY IN JURISDICTIONS
WHERE OFFERS AND SALES ARE PERMITTED. THE INFORMATION CONTAINED IN THIS
PROSPECTUS IS ACCURATE ONLY AS OF THE DATE OF THIS PROSPECTUS, REGARDLESS OF THE
TIME OF DELIVERY OF THE PROSPECTUS OR OF ANY SALE OF COMMON STOCK.
 
                          ---------------------------
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                     PAGE
                                     ----
<S>                                  <C>
Prospectus Summary.................    3
Risk Factors.......................    7
Reclassification...................   14
Use of Proceeds....................   15
Dividend Policy....................   15
Capitalization.....................   16
Dilution...........................   17
Selected Consolidated Financial
  Data.............................   18
Management's Discussion and
  Analysis of Financial Condition
  and Results of Operations........   20
Business...........................   32
Management.........................   43
Certain Transactions...............   49
Principal and Selling
  Stockholders.....................   50
Description of Capital Stock.......   51
Shares Eligible for Future Sale....   54
Underwriting.......................   57
Legal Matters......................   59
Experts............................   60
Additional Information.............   60
Index to Consolidated Financial
  Statements.......................  F-1
</TABLE>
 
                          ---------------------------
 
     Until              , 1999 (25 days after the date of this prospectus), all
dealers that effect transactions in these securities, whether or not
participating in this offering, may be required to deliver a prospectus. This is
in addition to the dealer's obligation to deliver a prospectus when acting as
underwriters and with respect to their unsold allotments or subscriptions.
------------------------------------------------------
------------------------------------------------------
------------------------------------------------------
------------------------------------------------------
 
                                               SHARES
 
                               [ONE SOURCE LOGO]
 
                                  COMMON STOCK
 

                            ------------------------
 
                                   PROSPECTUS
                                            , 1999
 
                            ------------------------


                            WILLIAM BLAIR & COMPANY
                         U.S. BANCORP PIPER JAFFRAY INC.
                          ADAMS, HARKNESS & HILL, INC.
 
------------------------------------------------------
------------------------------------------------------
<PAGE>   84
 
                                    PART II
 
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 13.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.
 
     Estimated expenses payable in connection with the sale of the common stock
in this offering are as follows:
 
<TABLE>
<S>                                                           <C>
SEC registration fee........................................  $ 11,259
NASD filing fee.............................................     4,550
Nasdaq National Market listing fee..........................    49,000
Printing and engraving expenses.............................   125,000
Legal fees and expenses.....................................   250,000
Accounting fees and expenses................................         *
Transfer agent and registrar fees and expenses..............         *
Miscellaneous...............................................         *
                                                              --------
     Total..................................................  $      *
                                                              ========
</TABLE>
 
------------
 
* To be completed by amendment
 
     OneSource will bear all of the expenses shown above.
 
ITEM 14.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
     The Delaware General Corporation Law, the Company's charter and by-laws
provide for indemnification of the Company's directors and officers for
liabilities and expenses that they may incur in such capacities. In general,
directors and officers are indemnified with respect to actions taken in good
faith in a manner reasonably believed to be in, or not opposed to, the best
interests of the Company, and with respect to any criminal action or proceeding,
actions that the indemnitee had no reasonable cause to believe were unlawful.
Reference is made to the Company's corporate charter and by-laws filed as
Exhibits 3.01 and 3.02 hereto, respectively.
 
     The Underwriting Agreement provides that the Underwriters are obligated,
under certain circumstances, to indemnify directors, officers and controlling
persons of the Company against certain liabilities, including liabilities under
the Securities Act. Reference is made to the form of Underwriting Agreement
filed as Exhibit 1.01 hereto.
 
     The Company intends to apply for a directors' and officers' insurance
policy.
 
ITEM 15.  RECENT SALES OF UNREGISTERED SECURITIES.
 
     In the three years preceding the filing of this registration statement, the
Company has issued the following securities that were not registered under the
Securities Act:
 
     Since January 1, 1996, the Company has issued options to purchase an
aggregate of 1,063,100 shares of common stock under the 1993 Plan, exercisable
at a weighted average price of $6.29 per share. From January 1, 1996 through
December 31, 1998, options to purchase 103,792 shares had been exercised. The
following table lists options granted between January 1, 1996 and March 1, 1999.
 
<TABLE>
<CAPTION>
DATE                                                          SHARES     PRICE
----                                                          ------     -----
<S>                                                           <C>        <C>
November 12, 1996...........................................  340,700    $2.78
November 12, 1996...........................................  280,000     4.45
April 17, 1997..............................................      600     2.78
July 17, 1997...............................................    1,000     2.78
</TABLE>
 
                                      II-1
<PAGE>   85
 
<TABLE>
<CAPTION>
DATE                                                          SHARES     PRICE
----                                                          ------     -----
<S>                                                           <C>        <C>
October 16, 1997............................................    1,000     2.78
November 12, 1997...........................................    8,000     2.78
November 17, 1997...........................................   70,000     2.78
November 17, 1997...........................................   64,000     4.45
May 6, 1998.................................................      900     2.78
May 6, 1998.................................................   99,800     4.45
February 26, 1999...........................................   20,000     4.45
February 26, 1999...........................................   15,000    12.00
February 26, 1999...........................................  162,100    20.20
</TABLE>
 
     No underwriters were involved in the foregoing sales of securities. Such
sales were made in reliance upon the exemption provided by Section 4(2) of the
Securities Act for transactions not involving a public offering and/or Rule 701
under the Securities Act.
 
ITEM 16.  EXHIBITS AND FINANCIAL STATEMENT SCHEDULES.
 
  (a) EXHIBITS:
 
<TABLE>
<CAPTION>
  EXHIBIT
    NO.                               EXHIBIT
  -------                             -------
  <C>       <S>
   +1.01    Form of Underwriting Agreement
   +3.01    Form of Restated Certificate of Incorporation of the Company
    3.02    Amended and Restated Certificate of Incorporation of the
            Company
    3.03    By-laws, as amended and restated, of the Company
   +3.04    Second Amended and Restated By-Laws of the Company
   +4.01    Specimen certificate representing the common stock
   +5.01    Opinion of Testa, Hurwitz & Thibeault, LLP
   10.01    1993 Stock Purchase and Option Plan
  +10.02    1999 Stock Option and Incentive Plan
  +10.03    1999 Employee Stock Purchase Plan
   10.04    Registration Agreement dated September 8, 1993
   10.05    Stock Purchase Warrant issued to Lotus Development
            Corporation dated September 8, 1993
   10.06    Warrant Agreement with Silicon Valley Bank dated September
            8, 1993
   10.07    Subordinated Promissory Note issued to Lotus Development
            Corporation dated September 8, 1993
   10.08    Stock Purchase Agreement dated September 8, 1993
   10.09    Form of Management Stock Purchase Agreement
   10.10    Stock Purchase Agreement dated August 3, 1993, by and among
            Lotus Development Corporation, Datext, Inc. and Datext
            Holding Corporation
   10.11    Lease dated July 1, 1998 by and between OneSource and
            CambridgePark Two Limited Partnership
   10.12    Lease dated January 20, 1999 by and between OneSource and
            300 Baker Avenue Associates, Limited Partnership
   10.13    Agreement and Plan of Merger dated February 26, 1999 by and
            between OneSource Information Services, Inc. and OneSource
            Holding Corporation
  +10.14    Stockholders Agreement dated September 8, 1993
   21.01    Subsidiaries of the Company
   23.01    Consent of Testa, Hurwitz & Thibeault, LLP (included in
            Exhibit 5.01)
   23.02    Consent of PricewaterhouseCoopers LLP
</TABLE>
 
                                      II-2
<PAGE>   86
 
<TABLE>
<CAPTION>
  EXHIBIT
    NO.                               EXHIBIT
  -------                             -------
  <C>       <S>
   24.01    Power of Attorney (included in signature page)
   27.01    Financial Data Schedule
</TABLE>
 
------------
+ to be filed by amendment
 
  (b) FINANCIAL STATEMENT SCHEDULES:
 
     Schedule II -- Valuation and Qualifying Accounts
 
     All other schedules for which provision is made in the applicable
accounting regulations of the Securities and Exchange Commission are either not
applicable or the required information is included in the Consolidated Financial
Statements and Notes thereto, and therefore have been omitted.
 
ITEM 17.  UNDERTAKINGS.
 
     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers and controlling persons of the Company
pursuant to provisions described in Item 14 above, or otherwise, the Company has
been advised that in the opinion of the Securities and Exchange Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Company of expenses
incurred or paid by a director, officer or controlling person of the Company in
the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Company will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.
 
     The Company hereby undertakes: (1) to provide to the underwriters at the
closing specified in the underwriting agreement, certificates in such
denominations and registered in such names as required by the underwriters to
permit prompt delivery to each purchaser; (2) that for purposes of determining
any liability under the Securities Act, the information omitted from the form of
prospectus filed as part of a registration statement in reliance upon Rule 430A
and contained in the form of prospectus filed by the registrant pursuant to Rule
424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part
of this registration statement as of the time it was declared effective; and (3)
that for the purpose of determining any liability under the Securities Act, each
post-effective amendment that contains a form of prospectus shall be deemed to
be a new registration statement relating to the securities offered therein, and
the offering of such securities at that time shall be deemed to be the initial
bona fide offering thereof.
 
                                      II-3
<PAGE>   87
 
                                   SIGNATURES
 
     Pursuant to the requirements of the Securities Act of 1933, the registrant
has duly caused this registration statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in Cambridge, Massachusetts on March 1,
1999.
 
                                          OneSource Information Services, Inc.
 
                                          By:     /s/ DANIEL J. SCHIMMEL
                                             -----------------------------------
                                             Daniel J. Schimmel
                                              President and Chief Executive
                                              Officer
 
                        POWER OF ATTORNEY AND SIGNATURES
 
     The undersigned officers and directors of OneSource Information Services,
Inc. hereby constitute and appoint Daniel J. Schimmel and Roy D. Landon, and
each of them singly, with full power of substitution, our true and lawful
attorneys-in-fact and agents to take any actions to enable OneSource Information
Services, Inc. to comply with the Securities Act, and any rules, regulations and
requirements of the Securities and Exchange Commission, in connection with this
registration statement, including the power and authority to sign for us in our
names in the capacities indicated below any and all amendments to this
registration statement and any other registration statement filed pursuant to
the provisions of Rule 462 under the Securities Act.
 
     Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.
 
<TABLE>
<CAPTION>
                SIGNATURE                                TITLE(S)                     DATE
                ---------                                --------                     ----
<S>                                         <C>                                   <C>
                                            President and Chief Executive         March 1, 1999
                                            Officer and Director (principal
          /s/ DANIEL J. SCHIMMEL            executive officer)
------------------------------------------
            Daniel J. Schimmel
 
                                            Vice President, Finance and           March 1, 1999
                                            Administration (principal
            /s/ ROY D. LANDON               financial officer)
------------------------------------------
              Roy D. Landon
 
             /s/ MARTIN KAHN                Director                              March 1, 1999
------------------------------------------
               Martin Kahn
 
            /s/ DAVID DOMINIK               Director                              March 1, 1999
------------------------------------------
              David Dominik
 
            /s/ GREGG NEWMARK               Director                              March 1, 1999
------------------------------------------
              Gregg Newmark
</TABLE>
 
                                      II-4
<PAGE>   88
 
                 SCHEDULE II--VALUATION AND QUALIFYING ACCOUNTS
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
<TABLE>
<CAPTION>
                                        BALANCE AT
                                       BEGINNING OF    CHARGED TO                       BALANCE AT
DESCRIPTION                               PERIOD       OPERATIONS    DEDUCTIONS(1)     END OF PERIOD
-----------                            ------------    ----------    --------------    -------------
<S>                                    <C>             <C>           <C>               <C>
Year ended December 31, 1996
  Reserves and allowances deducted
     from asset accounts
     Allowance for doubtful
        accounts.....................    $161,000        49,000          49,000          $161,000
Year ended December 31, 1997
  Reserves and allowances deducted
     from asset accounts
     Allowance for doubtful
        accounts.....................    $161,000        72,000          23,000          $210,000
Year ended December 31, 1998
  Reserves and allowances deducted
     from asset accounts
     Allowance for doubtful
        accounts.....................    $210,000       120,000          30,000          $300,000
</TABLE>
 
------------
(1) Doubtful accounts written off, net of recoveries
 
                                       S-1
<PAGE>   89
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
  EXHIBIT
    NO.
  -------
  <C>       <S>
   +1.01    Form of Underwriting Agreement
   +3.01    Form of Restated Certificate of Incorporation of the Company
    3.02    Amended and Restated Certificate of Incorporation of the
            Company
    3.03    By-laws, as amended and restated, of the Company
   +3.04    Second Amended and Restated By-Laws of the Company
   +4.01    Specimen certificate representing the common stock
   +5.01    Opinion of Testa, Hurwitz & Thibeault, LLP
   10.01    1993 Stock Purchase and Option Plan
  +10.02    1999 Stock Option and Incentive Plan
  +10.03    1999 Employee Stock Purchase Plan
   10.04    Registration Agreement dated September 8, 1993
   10.05    Stock Purchase Warrant issued to Lotus Development
            Corporation dated September 8, 1993
   10.06    Warrant Agreement with Silicon Valley Bank dated September
            8, 1993
   10.07    Subordinated Promissory Note issued to Lotus Development
            Corporation dated September 8, 1993
   10.08    Stock Purchase Agreement dated September 8, 1993
   10.09    Form of Management Stock Purchase Agreement
   10.10    Stock Purchase Agreement dated August 3, 1993, by and among
            Lotus Development Corporation, Datext, Inc. and Datext
            Holding Corporation
   10.11    Lease dated July 1, 1998 by and between OneSource and
            CambridgePark Two Limited Partnership
   10.12    Lease dated January 20, 1999 by and between OneSource and
            300 Baker Avenue Associates, Limited Partnership
   10.13    Agreement and Plan of Merger dated February 26, 1999 by and
            between OneSource Information Services, Inc. and OneSource
            Holding Corporation
  +10.14    Stockholders Agreement dated September 8, 1993
   21.01    Subsidiaries of the Company
   23.01    Consent of Testa, Hurwitz & Thibeault, LLP (included in
            Exhibit 5.01)
   23.02    Consent of PricewaterhouseCoopers LLP
   24.01    Power of Attorney (included in signature page)
   27.01    Financial Data Schedule
</TABLE>
 
------------
+ to be filed by amendment
[{"type": "S-1", "sequence": "1", "description": "ONSOURCE INFORMATION SERVICES", "secsgml_size_bytes": 308920}]
{"company-data": {"conformed-name": "ONESOURCE INFORMATION SERVICES INC", "cik": "0001079880", "assigned-sic": "", "irs-number": "043204522", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-1", "act": "33", "file-number": "333-73263", "film-number": "99555865"}, "business-address": {"street1": "150 CAMBRIDGE PARK DRIVE", "city": "CAMBRIDGE", "state": "MA", "zip": "02140", "phone": "6174417000"}, "mail-address": {"street1": "150 CAMBRIDGE PARK DRIVE", "city": "CAMBRIDGE", "state": "MA", "zip": "02140"}}
1
 
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MARCH 3, 1999
 
                                                     REGISTRATION NO. 333-
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
                            ------------------------
 
                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------
 
                      ONESOURCE INFORMATION SERVICES, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
                            ------------------------
DELAWARE                               7375                              04-3204522
    (STATE OR OTHER JURISDICTION         (PRIMARY STANDARD INDUSTRIAL               (I.R.S. EMPLOYER
 OF INCORPORATION OR ORGANIZATION)       CLASSIFICATION CODE NUMBER)             IDENTIFICATION NUMBER)
------------------------
 
                            150 CAMBRIDGEPARK DRIVE
                              CAMBRIDGE, MA 02140
                                  617-441-7000
         (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING
            AREA CODE, OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)
                            ------------------------
 
           DANIEL J. SCHIMMEL, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                      ONESOURCE INFORMATION SERVICES, INC.
                            150 CAMBRIDGEPARK DRIVE
                              CAMBRIDGE, MA 02140
                                  617-441-7000
            (NAME, ADDRESS INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
                   INCLUDING AREA CODE, OF AGENT FOR SERVICE)
                            ------------------------
                                   COPIES TO:
LAWRENCE S. WITTENBERG                                  KEVIN F. BLATCHFORD
           TESTA, HURWITZ & THIBEAULT, LLP                               SIDLEY & AUSTIN
                   125 HIGH STREET                                  ONE FIRST NATIONAL PLAZA
             BOSTON, MASSACHUSETTS 02110                             CHICAGO, ILLINOIS 60603
                 TEL: (617) 248-7000                                   TEL: (312) 853-7000
                 FAX: (617) 248-7100                                   FAX: (312) 853-7036
APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:  As soon
as practicable after the effective date hereof.
     If any of the securities being registered on this form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, check the following box.  [ ]
     If this form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, check the following box and
list the Securities Act registration statement number of the earlier effective
registration statement for the same offering.  [ ] _____________.
     If this form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ]____________.
     If this form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ] ____________.
     If delivery of the prospectus is expected to be made pursuant to Rule 434,
check the following box.  [X]
                            ------------------------
 
                        CALCULATION OF REGISTRATION FEE
-------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------
      TITLE OF EACH CLASS OF                  PROPOSED MAXIMUM
    SECURITIES TO BE REGISTERED          AGGREGATE OFFERING PRICE(1)         AMOUNT OF REGISTRATION FEE(1)
-------------------------------------------------------------------------------------------------------------
Common stock.......................            $40,500,000.00                         $11,259.00
-------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------
(1) Estimated solely to calculate the registration fee.
                            ------------------------
 
     THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933 OR UNTIL THIS REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
2
 
THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. WE MAY
NOT SELL THESE SECURITIES UNTIL THE REGISTRATION STATEMENT FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER
TO SELL THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY THESE 
SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.
 
                SUBJECT TO COMPLETION, DATED             , 1999
 
PROSPECTUS
 
                                             SHARES
 
                              [ONE SOURCE LOGO]
 
                                 COMMON STOCK
 
     OneSource Information Services, Inc. is offering            shares of its
common stock and the selling stockholders are offering            shares of
OneSource's common stock owned by them. We will not receive any of the proceeds
from the selling stockholders' sale of their shares.
 
     This is our initial public offering and no public market currently exists
for our shares. We expect the initial public offering price to be between
$           and $           per share. We intend to apply for quotation of the
common stock on the Nasdaq National Market under the symbol "ONES."
 
     INVESTING IN OUR COMMON STOCK INVOLVES CERTAIN RISKS. FOR MORE INFORMATION,
SEE "RISK FACTORS" ON PAGE 7.
                          ---------------------------
 
     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES, OR DETERMINED THAT
THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.
-----------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------
                                                            PER SHARE              TOTAL
-----------------------------------------------------------------------------------------------
Public Offering Price................................  $                    $
Underwriting Discount................................  $                    $
Proceeds to OneSource Information Services, Inc......  $                    $
Proceeds to Selling Stockholders.....................  $                    $
-----------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------
The Underwriters may also purchase at the public offering price, less the
underwriting discount, up to            additional shares from the selling
stockholders within 30 days from the date of this prospectus to cover any
over-allotments.
 
     We expect that the shares of the common stock will be ready for delivery on
or about              , 1999.
 
WILLIAM BLAIR & COMPANY
                        U.S. BANCORP PIPER JAFFRAY INC.
                                                    ADAMS, HARKNESS & HILL, INC.
 
               The date of this prospectus is              , 1999
3
 
     [The inside front cover depicts four computer screen shots of the OneSource
Business Browser. The heading on the page is "Ready-To-Use Business
Information." The top three computer screen shots depict the Global Business
Browser, the European Business Browser, and the UK Business Browser. The fourth
computer screen shot depicts Market Forecasts and contains a chart graphic.
There are four ellipses on the page that briefly describe the potential uses of
the business information contained in the Business Browser products, including:
"Profile a Company"; "Prospect for New Customers"; "Track Competitors"; and
"Research an Industry". The OneSource logo is in the lower right hand corner of
the page.]
 
                          ---------------------------
 
     OneSource(TM), Business Browser(TM), OneSource Business Browser(TM),
Business Browser AppLink(TM), AppLink(TM), and the OneSource logo are our
trademarks. Other trademarks and tradenames in this prospectus are the property
of their respective owners.

                          ---------------------------
 
     Unless the context otherwise requires, any reference to "OneSource" in this
prospectus means OneSource Information Services, Inc. and its subsidiary. Unless
otherwise indicated, all information contained in this prospectus:
 
        - reflects the merger on February 26, 1999 of OneSource Information
          Services, Inc. into its parent, OneSource Holding Corporation, and the
          name change of OneSource Holding Corporation to OneSource Information
          Services, Inc.
 
        - assumes no exercise of the Underwriters' over-allotment option
 
        - reflects the reclassification (prior to the completion of the
          offering) of each share of Class P common stock into one share of
          common stock plus            additional shares of common stock
          (determined by dividing the preference amount for each share of Class
          P common stock by the assumed initial public offering price)

                          ---------------------------
 
     This prospectus contains certain forward-looking statements that involve
substantial risks and uncertainties. When used in this prospectus, the words
"anticipate," "believe," "estimate," "intend" and "expect" and similar
expressions are intended to identify such forward-looking statements. Our actual
results, performance or achievements could differ materially from the results
expressed in or implied by these forward-looking statements. Factors that could
cause or contribute to such differences include those discussed in "Risk
Factors."
                                        2
4
 
                               PROSPECTUS SUMMARY
 
     This summary highlights information contained elsewhere in this prospectus.
It is not complete and does not contain all of the information that you should
consider before investing in our common stock. You should read the entire
prospectus carefully.
 
                                  THE COMPANY
 
     OneSource provides Web-based business and financial information to
professionals who need quick access to reliable corporate, industry and market
intelligence. Our Business Browser product line integrates comprehensive and
up-to-date business and financial information on over one million public and
private companies from more than 25 information providers drawing upon over
2,500 sources of content. These sources include both textual information, such
as news, trade press, SEC filings, executive biographies and analyst reports,
and numeric information, such as company financial results, stock quotes and
industry statistics. Our customers access this information over the Internet
using standard Web browsers at a fixed annual subscription price.
 
     According to an industry source, the market for all Web-based and on-line
business information services was $24.8 billion in 1997 and is projected to grow
to $39.8 billion in 2002, reflecting a compound annual growth rate of 9.9%.
According to this industry source, the primary market segment in which OneSource
participates--Web-based and on-line financial news, current awareness and
research services--was $5.4 billion in 1997 and is projected to grow to $9.8
billion in 2002, reflecting a compound annual growth rate of 12.6%. Recent
industry growth has been driven by corporations and other enterprises
recognizing that productivity and competitiveness depend on extensive knowledge
of external information, including information about industries, customers,
competitors, prospects, business trends, breaking news and market data.
 
     OneSource focuses on the functional uses of the business and financial
information it delivers. The Business Browser product line has been designed for
use not only by traditional users of business information, but also throughout
an organization, including sales, marketing, finance and management
professionals. We apply our knowledge of how business professionals use
information to transform raw, disparate data into meaningful, actionable
information. We focus on integrating and presenting information so that
interpretation, manipulation and analysis can be performed more easily by the
end user. Because our products are based on standard Web technology, our
customers require minimal installation and systems support, and users, after
minimal training, have full access to the products at any time from anywhere via
the Internet.
 
     Our products are designed to address information needs of leading
professional and financial services firms, technology companies and other large
organizations. Representative customers include American Express, Bain &
Company, BankAmerica, Boeing, British Telecom, Deloitte & Touche, Ernst & Young,
Harvard Business School, KPMG Peat Marwick, MCI/WorldCom, Merrill Lynch, Oracle
and SAP.
 
     OneSource's fixed annual pricing strategy is designed to be particularly
attractive to large organizations. The annual subscription price for the
Business Browser product line declines on a per-user basis as the total number
of users increases. The fixed-price model encourages professionals to use the
products as needed without concern with additional, usage-based charges,
                                        3
5
 
and a declining marginal price per user encourages customers to distribute the
products widely throughout their organizations.
 
     At December 31, 1998, 445 organizations subscribed to our Web-based
Business Browser product line, up from 233 at December 31, 1997. On average, our
customers for Web-based products at December 31, 1998 had an annualized contract
value of $58,248 per customer, compared to $38,512 per customer at December 31,
1997. The annualized value of Business Browser customer contracts was $25.9
million at December 31, 1998, having grown from $9.0 million at the end of 1997.
Of this $25.9 million, $14.2 million was attributable to those customers that
were under contract at both December 31, 1997 and 1998. The renewal rate of the
Business Browser product line for 1998 was 90% calculated on a dollar basis. For
more information regarding annualized contract value, see "Management's
Discussion and Analysis of Financial Condition and Results of Operations."
 
     Our goal is to become a leading Web-based provider of business and
financial information to professionals worldwide. Our strategy to accomplish
this objective includes:
 
        - focusing on the information needs of professionals in large
          organizations
 
        - expanding our customer base through our sales and marketing efforts
 
        - leveraging our existing customer base by expanding the number of users
          per customer and upgrading those customers to new or enhanced products
 
        - continually expanding the content and functionality of our products
          and designing additional products
 
        - selectively seeking possible strategic acquisitions and alliances
 
                                  THE OFFERING
Shares offered by OneSource..............
Shares offered by the selling
  stockholders...........................  
Shares outstanding immediately after the
  offering...............................        (1)
Use of proceeds..........................  Repayment of outstanding debt, repurchase
                                           of certain common stock in connection
                                           with the reclassification, payments to
                                           terminate management fee arrangements and
                                           general corporate purposes, including
                                           working capital and possibly to acquire
                                           or invest in complementary businesses,
                                           products or technologies
Proposed Nasdaq National Market symbol...  ONES
------------
(1) Based on shares of common stock outstanding as of           , 1999. Excludes
                shares of common stock issuable upon the exercise of stock
    options and warrants outstanding on           , 1999 with a weighted average
    exercise price of $        and an aggregate of     shares reserved for
    future stock option grants and purchases under our equity compensation
    plans. For more information, see "Description of Capital Stock,"
    "Management--Equity Plans" and Notes 6, 7 and 8 to the Consolidated
    Financial Statements.
                                        4
6
 
                      SUMMARY CONSOLIDATED FINANCIAL DATA
      (IN THOUSANDS, EXCEPT PER SHARE, SHARE AND NUMBER OF CUSTOMERS DATA)
YEAR ENDED DECEMBER 31,
                                                        -----------------------------
                                                         1996       1997       1998
                                                        -------    -------    -------
STATEMENT OF OPERATIONS DATA:
Web-based product revenues............................  $    15    $ 3,312    $16,058
CD Rom product revenues(1)............................   30,419     27,072     14,370
                                                        -------    -------    -------
  Total revenues......................................   30,434     30,384     30,428
                                                        =======    =======    =======
Gross profit..........................................   17,895     17,539     16,773
Operating expenses....................................   19,488     18,943     21,737
                                                        -------    -------    -------
Loss from operations..................................   (1,593)    (1,404)    (4,964)
Interest income (expense), net........................     (733)      (930)      (595)
Gain on sale of product line..........................       --        501     12,797
                                                        -------    -------    -------
Income (loss) before income taxes and extraordinary
  gain................................................   (2,326)    (1,833)     7,238
                                                        =======    =======    =======
Net income (loss).....................................  $(1,933)   $(1,833)   $ 6,988
                                                        =======    =======    =======
Unaudited pro forma earnings per share:(2)
  Basic...............................................                        $
  Diluted.............................................                        $
  Weighted average common shares outstanding:
     Basic............................................
     Diluted..........................................
DECEMBER 31, 1998
                                                              ------------------------------
                                                                                UNAUDITED
                                                                                PRO FORMA
                                                                 ACTUAL       AS ADJUSTED(3)
                                                              ------------    --------------
BALANCE SHEET DATA:
Cash and cash equivalents...................................    $ 8,665           $
Working capital (deficit)...................................     (2,118)
Total assets................................................     27,646
Total debt (including capital lease obligations)............      6,936               704
Deferred revenues...........................................     18,022            18,022
Total stockholders' equity (deficit)........................     (6,311)
DECEMBER 31,
                                                        -----------------------------
                                                         1996       1997       1998
                                                        -------    -------    -------
OTHER DATA FOR WEB-BASED PRODUCTS (UNAUDITED):
Annualized contract value(4)..........................  $   412    $ 8,973    $25,920
Number of customers...................................       11        233        445
Average annualized contract value per customer........  $  37.4    $  38.5    $  58.2
------------
(1) In 1997 and 1998, OneSource divested certain CD Rom product lines. Revenues
    attributable to these divested product lines, which are included in the
    statement of operations data through the divestiture date, were $6,415,000,
    $6,630,000 and $2,612,000 in the years ended December 31, 1996, 1997 and
    1998, respectively.
 
(2) Unaudited pro forma basic and diluted earnings per share of common stock for
    the year ended December 31, 1998 have been calculated based on net income
    attributable to all classes of common stock and assuming the
    reclassification of OneSource's
                                        5
7
 
    Class P common stock prior to completion of this offering as if it had
    occurred at January 1, 1998. In the reclassification, each share of Class P
    common stock will be reclassified into one share of common stock plus an
    additional number of shares of common stock (determined by dividing the
    preference amount for such share by the assumed initial public offering
    price of $        per share). As described in "Use of Proceeds", OneSource
    intends to use a portion of its net proceeds to repay a $6.2 million note
    due to Lotus Development Corporation and to pay $1.0 million to terminate
    certain management fee arrangements. Accordingly, had the note repayment and
    the management fee termination occurred at January 1, 1998, unaudited
    supplemental pro forma basic and diluted earnings per share for the year
    ended December 31, 1998 would be $        and $        , respectively. Such
    amounts reflect the elimination of annual interest expense on the note of
    $0.5 million and the elimination of annual management fees of $0.2 million,
    and the issuance of             shares of common stock at the assumed
    initial public offering price of $        per share necessary to fund the
    note repayment and management fee termination.
 
(3) This column shows the numbers in the "Actual" column as adjusted to give
    effect to:
 
    - the reclassification of each share of OneSource's Class P common stock
      prior to the completion of this offering into one share of common stock
      plus an additional number of shares of common stock (determined by
      dividing the preference amount as of December 31, 1998 for such share by
      the assumed initial public offering price of $        per share);
 
    - the sale of       shares of common stock by OneSource in this offering at
    the assumed initial public offering price of $
     per share, as if the sale had been completed on December 31, 1998;
 
    - the use of a portion of the estimated net proceeds to OneSource from this
      offering to pay off the note due to Lotus Development Corporation for $6.2
      million plus accrued interest as of December 31, 1998 of $0.5 million;
 
    - the use of a portion of the estimated net proceeds to OneSource from this
      offering to repurchase for $        million         shares of common stock
      which were issued to holders of Class P common stock in satisfaction of
      their preference amount; and
 
    - the use of a portion of the estimated net proceeds to OneSource from this
      offering to pay $1.0 million to terminate certain management fee
      arrangements.
 
    For more information, see "Reclassification," "Use of Proceeds" and
"Capitalization."
 
(4) Annualized contract value represents the invoiced fees for one month for all
    customer contracts for Web-based products in effect at the measurement date,
    multiplied by 12, without regard to the actual remaining duration of such
    contracts. At December 31, 1996, 1997 and 1998, annualized contract value
    was calculated by multiplying the total amount of fees invoiced for one
    month and included in deferred revenues for all customer contracts for
    Web-based products at December 31, 1996, 1997 and 1998 of $34,300, $747,750
    and $2,160,000, respectively, by 12. For more information regarding
    annualized contract value, see "Management's Discussion and Analysis of
    Financial Condition and Results of Operations."
 
                            ------------------------
 
     OneSource was incorporated in Delaware on July 21, 1993 under the name
Datext Holding Corporation. On February 26, 1999, OneSource Information
Services, Inc. merged into its parent, OneSource Holding Corporation, and the
name of the combined company was changed to OneSource Information Services, Inc.
Our principal executive offices are located at 150 CambridgePark Drive,
Cambridge, MA 02140, and our telephone number is (617) 441-7000.

                                        6
8
 
                                  RISK FACTORS
 
     You should consider carefully the risks described below before you decide
to buy our common stock. The risks and uncertainties described below are not the
only ones we face. Additional risks and uncertainties that we do not presently
know about or that we currently believe are immaterial may also adversely impact
our business operations.
 
     If any of the following risks actually occur, our business, financial
condition or results of operations would likely suffer. In such case, the
trading price of our common stock could fall, and you may lose all or part of
the money you paid to buy our common stock.
 
     This prospectus also contains forward-looking statements that involve risks
and uncertainties. Our actual results could differ significantly from those
anticipated in these forward-looking statements as a result of certain factors,
including the risks we face, as more fully described below in this section and
elsewhere in this prospectus.
 
OUR BUSINESS BROWSER PRODUCTS HAVE NOT BEEN PROFITABLE
 
     We began operations as an independent company in 1993. We began to migrate
our business to the Web from CD Rom-based products in early 1996, and launched
the Web-based Business Browser product line in December 1996. Our prospects must
be considered in light of the risks, expenses and difficulties frequently
encountered by companies transitioning to a new product line, particularly
companies in the new and rapidly evolving market for Internet and Web-based
business information products. We incurred losses from operations of
approximately $1.6 million in 1996, $1.4 million in 1997 and $5.0 million in
1998. In addition, we have not reached the critical mass of users of Web-based
products which we believe is necessary to leverage effectively our
infrastructure expenses and become profitable. As of December 31, 1998, we had
an accumulated deficit of $10.4 million.
 
WE RELY PRIMARILY ON OUR BUSINESS BROWSER PRODUCT LINE
 
     Subscription revenues from our Business Browser product line accounted for
83% of our total annualized contract value at the end of 1998 and 29% at the end
of 1997. We are currently phasing out CD Rom products that are not part of the
Business Browser product line. As a result, our future financial condition will
depend heavily on the success or failure of our Business Browser product line.
Business Browser products were introduced in December 1996 and it is difficult
to predict demand and market acceptance for these products in the new and
rapidly evolving Web-based business information services market. If the demand
for Business Browser products does not grow, whether due to competition, lack of
market acceptance, failure of Internet or Web use to grow in general,
technological change or other factors, our business would suffer significantly.
 
WE FACE INTENSE COMPETITION
 
     The business information services industry is intensely competitive. We
face direct or indirect competition from the following types of companies:
 
        - large, well-established business and financial information providers
          such as Dow Jones, Dialog, Lexis-Nexis, Pearson, Reuters, Thomson,
          Primark and McGraw-Hill
 
                                        7
9
 
        - on-line information services or Websites targeted to specific markets
          or applications, such as NewsEdge, Factset and Bloomberg
 
        - providers of sales, marketing and credit information such as Dun &
          Bradstreet
 
        - Web retrieval, Web "portal" companies and other free or low-cost mass
          market on-line services such as Excite, Infoseek, Lycos, Yahoo! and
          AOL/Netscape
 
     Many of our existing competitors, as well as a number of prospective
competitors, have longer operating histories, greater name recognition, larger
customer bases and significantly greater financial, technical and marketing
resources than we do. As a result, they may be able to respond more quickly to
new or emerging technologies and changes in user requirements, or to devote
greater resources to the development, promotion and sale of their products than
we can. Such competitors may be able to undertake more extensive marketing
campaigns, adopt more aggressive pricing policies and make more attractive
offers to potential employees, customers and information providers. Our
competitors also may develop products that are equal or superior to our products
or that achieve greater market acceptance than our products.
 
     Certain of our competitors offer financial and business information free of
charge with the goal of achieving high enough usage to facilitate the sale of
substantial amounts of advertising. To the extent these types of competitors
offer products free of charge that are similar to ours, it would have a material
adverse impact on our business, financial condition and results of operations.
In addition, there are relatively low barriers to entry to the Web-based
information market and we may face additional competition from new entrants. We
also expect that competition may increase as a result of industry consolidation.
It is possible that new competitors may emerge and rapidly acquire significant
market share. Increased competition is likely to result in price reductions,
reduced gross margins and loss of market share. Any of these would have a
material adverse effect on our business, financial condition and results of
operations.
 
WE DEPEND ENTIRELY ON OUR INFORMATION PROVIDERS FOR CONTENT
 
     We do not own or create the original content distributed through our
products. We depend on information providers to supply information and data
feeds to us on a timely basis. Our products could experience interruptions due
to any failure or delay in the transmission or receipt of this information.
 
     Many of our information providers compete with one another and, in some
cases, with us, for users. Business decisions made by our information providers
could adversely affect the availability or pricing of their information to us.
Any increase in the fees we negotiate with our information providers could have
an adverse effect on our results of operations.
 
     Our arrangements with our information providers generally extend for
one-year periods, which automatically renew unless terminated by notice given at
least three months prior to the end of the term. In the event of a breach by us,
the contracts can be terminated on relatively short notice. An information
provider may be difficult to replace and the loss of one or more significant
information providers could decrease the quality, quantity or mix of the
information distributed through our products. This could make our products less
competitive. If information providers terminate their relationships with us, our
business and delivery of our products may be disrupted. This could result in a
loss of customers or requests for refunds.
 
                                        8
10
 
IF OUR WEBSITE SERVICE IS DISRUPTED, OUR BUSINESS WOULD BE ADVERSELY AFFECTED
 
     Our on-line site is located at a dedicated hosting facility and we do not
currently have a shadow site fully equivalent to the live on-line site. Any
damage to the hosting facility or the equipment there, such as damage by fire or
power loss, or loss of telecommunications could disrupt the delivery of our
products. In addition, our users depend on Internet service providers, on-line
service providers and other Website operators for access to our products. Each
of them has experienced significant outages in the past, and could experience
outages, delays and other difficulties due to system failures unrelated to our
on-line architecture. These types of occurrences could cause users to perceive
our products as not functioning properly and therefore cause them to use other
methods to obtain their business and financial information.
 
     The number of Business Browser users has increased since its introduction
in December 1996 and we are seeking to further increase our user base. This has
led to increased usage and increased demands on our on-line architecture. Any
downtime or slow response times may damage our reputation and make it more
difficult to attract new users.
 
OUR MARKET IS NEW AND RAPIDLY EVOLVING
 
     The market for Web-based distribution of electronic business and financial
information has only recently begun to develop and it is rapidly evolving. This
makes it difficult to predict demand and market acceptance for our products. We
cannot guarantee that the market for our products will grow or that our products
will become widely accepted. If the market for our products does not develop as
quickly as we expect or if our products are not accepted by customers, our
future financial results will be adversely affected. A significant increase in
the number of customers and development of new product offerings could also
require the expenditure of significant amounts of money, time and other
resources. This could strain our personnel and financial resources.
 
WE DEPEND ON CONTINUED GROWTH IN INTERNET USE
 
     Our business would be adversely affected if the number of professionals
using the Web does not continue to grow. This growth may be inhibited by a
number of factors, such as:
 
        - inadequate network infrastructure
 
        - inconsistent quality of service
 
        - lack of cost-effective, high-speed service
 
        - security concerns
 
     Even if Web use grows, the Internet infrastructure may not be able to
support adequately future growth and its reliability and quality of service may
suffer. In addition, numerous Websites have experienced service interruptions
due to outages and other delays occurring internally and throughout the Internet
network infrastructure. If these outages or delays occur frequently in the
future, Web usage, as well as usage of our products, could grow more slowly or
decline.
 
GOVERNMENT REGULATION AND LEGAL UNCERTAINTIES RELATING TO THE WEB COULD HURT OUR
BUSINESS
 
     Currently, there are few laws or regulations that specifically regulate
communications or commerce on the Web. However, laws and regulations may be
adopted that address issues such
 
                                        9
11
 
as user privacy, pricing and the characteristics and quality of products and
services. For example, the Telecommunications Act sought to prohibit the
transmission of certain types of information and content over the Web. In
addition, several telecommunications companies have petitioned the Federal
Communications Commission to regulate Internet and on-line service providers in
a manner similar to long distance telephone carriers and to impose access fees
on such providers. This could increase the cost of transmitting data over the
Internet. Moreover, it may take years to determine the extent to which existing
laws relating to issues such as property ownership, libel and personal privacy
apply to the Web. Finally, state tax laws and regulations relating to the
provision of products and services over the Internet are still developing. If
individual states impose taxes on products and services provided over the Web,
the cost of our products may increase and we may not be able to increase the
price we charge for our products to cover these costs. Any new laws or
regulations or new interpretations of existing laws and regulations relating to
the Web could adversely affect our business.
 
WE RELY ON OUR INTELLECTUAL PROPERTY
 
     We believe that our success depends, in large part, on protecting our
intellectual property in the United States and in foreign countries. Other than
certain trademarks, most of our intellectual property consists of proprietary or
confidential information that is not subject to patent or similar protection.
Competitors may independently develop similar or superior products, software or
business models.
 
     We cannot guarantee that we will be able to protect our intellectual
property. There is no way to assure that unauthorized third parties will not try
to copy our products or business model or use our confidential information to
develop competing products. Legal standards relating to the validity,
enforceability and scope of protection of certain proprietary rights in
Internet-related businesses are uncertain and still evolving. As a result, we
cannot predict the future viability or value of our proprietary rights and those
of other companies within the industry. We also cannot guarantee that our
business activities and products will not infringe upon the proprietary rights
of others, or that other parties will not assert infringement claims against us.
Any such claims and any resulting litigation, should it occur, could subject us
to significant liability for damages and could result in invalidation of our
proprietary rights. Even if we eventually won any such litigation, it could be
time-consuming and expensive to defend, and could result in the diversion of our
management's time and attention.
 
WE COULD BE SUBJECT TO LEGAL LIABILITY FOR DISTRIBUTING INFORMATION ON OUR
WEBSITE
 
     We may be subjected to claims based on negligence or other theories
relating to the information we distribute. Similarly, we may be subjected to
claims for defamation or copyright or trademark infringement relating to the
information we provide in our products. These types of claims have been brought,
sometimes successfully, against on-line services as well as print publications
in the past. We also could be subjected to claims based upon the content that is
accessible from our products through links to other Websites. These types of
claims could be time-consuming and expensive to defend, and could result in the
diversion of our management's time and attention. In addition, if our products
provide faulty or inaccurate information, or fail to provide all the information
a user expects, we could be subject to legal liability. Our insurance and
contractual provisions with users and information providers may not protect us
against these types of claims.
 
                                       10
12
 
OUR PRODUCTS COULD CONTAIN SOFTWARE DEFECTS
 
     Complex software like the software we develop for our products may contain
errors or defects, especially when first implemented, that may be very costly to
correct. Defects or errors also could result in downtime and our business could
suffer significantly from potential adverse customer reaction, negative
publicity and harm to our reputation.
 
WE MAY EXPERIENCE SIGNIFICANT FLUCTUATIONS IN OUR QUARTERLY RESULTS
 
     Our quarterly revenues, gross profits and results of operations have
fluctuated significantly in the past and we expect them to continue to fluctuate
significantly in the future. In addition, we believe that an important measure
of our business is the annualized contract value at the end of each period,
which also may fluctuate. Causes of such fluctuations have included and may
include, among other factors:
 
        - changes in demand for our products
 
        - the dollar value and timing of both new and renewal subscriptions
 
        - competition (particularly price competition)
 
        - changes in operating expenses
 
        - technical difficulties or system downtime affecting our products on
          the Web generally
 
        - economic conditions specific to the Web, as well as general economic
          conditions
 
        - consolidation of our customers
 
     In addition, a substantial portion of our expenses, including certain
product development and selling and marketing expenses, must be incurred in
advance of revenue generation. If our projected revenue does not meet our
expectations, then we may have an operating loss in a particular quarter.
 
     Any one or more of these factors could affect our business, financial
condition and results of operations, and this makes the prediction of results of
operations on a quarterly basis unreliable. As a result, we believe that
period-to-period comparisons of our historical results of operations and
annualized contract values are not necessarily meaningful and that you should
not rely on them as an indication for future performance. Also, due to these and
other factors, it is possible that our quarterly results of operations
(including the annualized contract value) may be below the expectations of
public market analysts and investors. If this happens, the price of our common
stock would likely decrease.
 
WE DEPEND ON KEY PERSONNEL
 
     Our future success depends on the continued services of a number of key
employees, including Daniel J. Schimmel, our President and Chief Executive
Officer, James A. Becker, our Vice President, Global Strategic Web Applications
Team, Philip J. Garlick, our Vice President, Global Enterprise Sales and
Marketing, Mark C. VanDine, our Vice President, Engineering and Roy D. Landon,
our Vice President, Finance and Administration. We also depend on a limited
number of engineers to monitor the performance and availability of our complex
network and to perform the necessary updates and repairs. We do not have
employment contracts with our key personnel. If any of our key employees leave,
the loss of their technological knowledge and industry expertise would seriously
impede the development of new products and services and our
 
                                       11
13
 
ability to manage our business. The loss of one or a group of our key employees
could adversely affect our future financial results.
 
THERE IS INTENSE COMPETITION FOR QUALIFIED PERSONNEL
 
     Our future performance also depends upon our ability to attract and retain
highly-qualified technical, sales and managerial personnel. Qualified personnel
are in great demand throughout the software and Internet industries and there is
intense competition for such personnel. In addition, competition for qualified
personnel may lead to increased costs for such personnel. If we do not succeed
in retaining our personnel or in attracting new employees, our business could
suffer significantly.
 
WE ARE SUBJECT TO RISKS OF OPERATING INTERNATIONALLY
 
     Revenue from customers located outside North America accounted for 23% in
1998, 20% in 1997 and 17% in 1996 of our total revenue for such years. Over
time, we expect revenue from international operations, principally in Europe, to
increase as a percentage of our total revenue. As a result, we may be exposed to
a number of risks customary for international operations, including:
 
        - difficulties relating to managing an international sales force
 
        - the burdens of complying with a wide variety of foreign laws
 
        - the uncertainty of laws and enforcement in certain countries relating
          to the protection of intellectual property
 
        - multiple and possibly overlapping tax structures
 
        - economic or political changes in international markets
 
        - currency and exchange rate fluctuations
 
        - adverse tax consequences of returning any earnings of our foreign
          operations back to the United States
 
     To date, we have not used risk management techniques or "hedged" the risks
associated with fluctuations in foreign exchange rates.
 
WE ARE SUBJECT TO RISKS ASSOCIATED WITH YEAR 2000 PROBLEMS
 
     Many existing computer systems and software products do not properly
recognize dates after December 31, 1999. This "Year 2000" problem could result
in miscalculations, data corruption, system failures or disruptions of
operations. We are subject to potential Year 2000 problems affecting
telecommunication services, customers, our products, our internal systems and
the systems of our hosting facility and our information providers, any of which
could have a material adverse effect on our business, financial condition and
results of operations. We also have identified certain third-party software as
non-compliant and certain internal systems need to be addressed as part of our
relocation in June 1999. For more information, see "Management's Discussion and
Analysis of Financial Condition and Results of Operations--Year 2000 Readiness
Disclosure Statement." Furthermore, as we approach the Year 2000, customers may
be forced to devote greater resources to comply with Year 2000 requirements and
as a result purchase fewer products from us, which would have an adverse effect
on our net revenues.
 
                                       12
14
 
OUR EXISTING OFFICERS AND DIRECTORS WILL CONTINUE TO CONTROL ONESOURCE
 
     Following this offering, our officers and directors, together with entities
affiliated with them, will beneficially own approximately      % of our
outstanding shares of common stock (     % if the over-allotment option is
exercised in full). As a result, these stockholders acting together will be able
to take any of the following actions without the approval of our public
stockholders:
 
        - elect our directors
 
        - amend our charter or approve a merger, sale of assets or other major
          corporate transaction
 
        - defeat any non-negotiated takeover attempt that may be beneficial to
          our public stockholders
 
        - otherwise control the outcome of all matters submitted for a
          stockholder vote
 
THE OFFERING WILL BENEFIT SELLING STOCKHOLDERS
 
     The selling stockholders will receive substantial proceeds and certain
other benefits in connection with this offering. In addition, a selling
stockholder and an affiliate of another selling stockholder will each receive a
payment of $0.5 million out of OneSource's net proceeds to terminate a
management fee arrangement. For more information, see "Certain Transactions."
The offering will also establish a public market for the common stock and
provide significantly increased liquidity to our existing stockholders and
optionholders.
 
THERE IS NO PRIOR TRADING MARKET FOR OUR COMMON STOCK
 
     Before this offering, there was no public market for our common stock. We
and the underwriters have determined the initial public offering price of our
common stock based on negotiations between us concerning the proper valuation of
our common stock. Nevertheless, after this offering, you may not be able to
resell your shares at or above the initial public offering price due to a number
of factors, including:
 
        - actual or anticipated fluctuations in our operating results or
          annualized contract values
 
        - changes in expectations as to our future financial performance
 
        - changes in securities analysts' financial estimates
 
        - the operating and stock price performance of our competitors and other
          comparable companies
 
     In addition, the stock market in general, and the stocks of Web-based
businesses in particular, have experienced extreme volatility that often has
been unrelated to the operating performance of particular companies. These broad
market and industry fluctuations may adversely affect the trading price of our
common stock, regardless of our actual operating performance. You should read
the "Underwriting" section for a more complete discussion of the factors that
the underwriters and we considered in determining the initial public offering
price.
 
OTHER SHARES MAY BE SOLD IN THE FUTURE
 
     After this offering, we will have                 shares of common stock
outstanding and will have reserved an additional                 shares of
common stock for issuance pursuant to our stock option and purchase plans and
outstanding warrants. We intend to register for resale the shares of common
stock reserved for issuance under our stock option and stock purchase plans
approximately 180 days after the date of this prospectus. The federal securities
laws impose
 
                                       13
15
 
certain restrictions on the ability of certain stockholders to resell their
shares. In addition, our officers and directors have agreed not to sell their
shares for a period of 180 days after the date of this prospectus.
 
     If a large number of our shares of common stock are sold following this
offering, the price of our common stock would likely decrease.
 
PURCHASERS WILL INCUR IMMEDIATE AND SUBSTANTIAL DILUTION
 
     The initial public offering price of our common stock is substantially
higher than the resulting net tangible book value per share of the outstanding
common stock after the offering. Accordingly, if you purchase any shares of
common stock in this offering you will incur immediate dilution of approximately
$           in the net tangible book value per share of the common stock from
the price you pay for our common stock.
 
OUR ANTI-TAKEOVER PROVISIONS MAY HAVE ADVERSE EFFECTS
 
     Our Restated Certificate of Incorporation and Amended and Restated By-laws
contain anti-takeover provisions that could have the effect of delaying or
preventing changes in our management, even if such changes would benefit our
public stockholders. For example, following the closing of this offering, the
Board of Directors may issue up to one million shares of preferred stock without
any further vote or action by the stockholders. The preferred stock could have
voting, liquidation, dividend and other rights superior to those of the common
stock, and, therefore, any issuance of preferred stock could adversely affect
your rights as a common stockholder. These factors could cause the market price
of the common stock to decrease.
 
WE DO NOT EXPECT TO PAY DIVIDENDS
 
     We do not expect to pay cash dividends on our common stock in the
foreseeable future.
 
                                RECLASSIFICATION
 
     Prior to the consummation of this offering, OneSource will reclassify all
of its outstanding shares of capital stock into a single class of common stock
and will authorize a single class of undesignated preferred stock. Each share of
Class P common stock will be reclassified into shares of common stock. Each
share of Class P common stock is entitled to a payment upon any distribution by
OneSource to holders of its capital stock in an amount equal to the original
cost of such share plus a preferential amount which accrues on a daily basis at
a rate of 12% per annum on such cost, compounded quarterly. As of              ,
1999, the preference amount of the outstanding Class P common stock will be
$           per share, based on an original cost per share of $           for an
aggregate preference of $           million. In connection with the
reclassification, each outstanding share of Class P common stock will be
reclassified into one share of common stock plus an additional number of shares
of common stock determined by dividing the applicable preference amount for such
share by the value of a share of common stock based on the initial public
offering price in the offering. Based on an assumed initial public offering
price of $           per share, an aggregate of            shares of common
stock will be issued upon the reclassification of all shares of Class P common
stock. Fractional shares otherwise issuable will be rounded down to the nearest
whole number. OneSource intends to repurchase the shares of common stock issued
with respect to the preference amount at the initial public offering price upon
completion of this offering. For more information, see "Use of Proceeds."
 
                                       14
16
 
                                USE OF PROCEEDS
 
     We estimate our net proceeds from the issuance and sale of the
                shares of common stock being offered by OneSource hereby to be
approximately $           million, at an assumed initial public offering price
of $     per share, after deducting the estimated underwriting discount and
offering expenses. We will not receive any proceeds from the sale of the common
stock by the selling stockholders.
 
     The principal purposes of this offering are to repay debt, repurchase
certain shares of common stock in connection with the reclassification,
terminate certain management fee arrangements, obtain working capital, establish
a public market for our common stock, increase our visibility in the
marketplace, facilitate future access to public capital markets and provide
liquidity to existing stockholders and optionholders. We intend to use
approximately $6.7 million of the net proceeds to us to repay principal and
interest on a note issued by OneSource to Lotus Development Corporation in
connection with the purchase of OneSource's business from Lotus in 1993. The
note bears interest at the rate of 8% per year and is due September 8, 2000,
unless accelerated upon certain events. The completion of this offering would
require OneSource to repay a significant portion of the note if we do not repay
it in full. We also intend to use approximately $           million to
repurchase            shares of common stock issued to holders of Class P common
stock in the reclassification in satisfaction of their preference amount. For
more information, see "Reclassification." In addition, we intend to pay $0.5
million to each of William Blair Venture Partners III Limited Partnership and an
affiliate of Information Partners Capital Fund, L.P. to terminate certain
management fee arrangements. For more information, see "Certain Transactions."
 
     We intend to use the remaining net proceeds for general corporate purposes,
including working capital, and we may also use a portion of the net proceeds to
acquire or invest in complementary businesses or products or to obtain the right
to use complementary technologies. We have no specific understandings,
commitments or agreements with respect to any such acquisition or investment.
Pending such uses, our remaining net proceeds of the offering will be invested
in short-term, interest-bearing, investment-grade securities, certificates of
deposit or direct or guaranteed obligations of the United States.
 
                                DIVIDEND POLICY
 
     We have never paid any cash dividends on our common stock and do not
anticipate paying any cash dividends in the foreseeable future.
 
                                       15
17
 
                                 CAPITALIZATION
 
     The left-hand column in the following table sets forth OneSource's
capitalization as of December 31, 1998. The middle column gives pro forma effect
to the reclassification of each outstanding share of OneSource's Class P common
stock into one share of common stock plus an additional number of shares of
common stock (determined by dividing the applicable preference amount as of
December 31, 1998 for such share by the value of a share of common stock based
on the assumed initial public offering price of $           per share) and the
filing of our Restated Certificate of Incorporation, each prior to the
completion of this offering. The right-hand column sets forth OneSource's pro
forma capitalization as of December 31, 1998, as further adjusted to reflect the
sale of                 shares of common stock by OneSource in this offering
(based on an assumed initial public offering price of $     per share), the use
of a portion of the estimated net proceeds to repay the $6.2 million note plus
accrued interest of $0.5 million as of December 31, 1998 payable to Lotus, to
repurchase for $  million   shares of common stock issued to holders of Class P
common stock in satisfaction of their preference amount, to pay $1.0 million to
terminate certain management fee arrangements, all as if they occurred on
December 31, 1998. You should read the data set forth below in conjunction with
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" and the Consolidated Financial Statements and Notes thereto
appearing elsewhere in this prospectus.
DECEMBER 31, 1998
                                                            --------------------------------------
                                                                                        PRO FORMA
                                                                         PRO FORMA     AS ADJUSTED
                                                             ACTUAL     (UNAUDITED)    (UNAUDITED)
                                                            --------    -----------    -----------
Current portion of capital lease obligations(1)...........  $    471      $    471      $    471
                                                            ========      ========      ========
Long-term debt and capital lease obligations(1)...........     6,465         6,465           233
                                                            --------      --------      --------
Stockholders' equity (deficit):
  Preferred stock, $0.01 par value; no shares authorized,
     issued or outstanding, actual; 1,000,000 shares
     authorized, no shares issued or outstanding, pro
     forma; 1,000,000 shares authorized, no shares issued
     or outstanding, pro forma as adjusted................        --            --            --
  Class P common stock, $0.01 par value; 500,000 shares
     authorized, 352,400 shares issued and outstanding,
     actual; no shares authorized, issued or outstanding,
     pro forma; no shares authorized, issued or
     outstanding, pro forma as adjusted...................     3,524            --            --
  Common stock, $0.01 par value; 6,500,000 shares
     authorized, 3,329,392 shares issued and 3,275,392
     shares outstanding, actual; 20,000,000 shares
     authorized,                shares issued and
                    shares outstanding, pro forma;
     20,000,000 shares authorized,                issued
     and                shares outstanding, pro forma as
     adjusted(2)..........................................        33
  Additional paid-in capital..............................       759
  Unearned compensation...................................       (39)          (39)          (39)
  Accumulated deficit.....................................   (10,444)      (10,444)      (11,444)
  Accumulated other comprehensive loss....................      (138)         (138)         (138)
  Common stock held in treasury...........................        (6)           (6)
                                                            --------      --------      --------
     Total stockholders' equity (deficit).................    (6,311)
                                                            --------      --------      --------
          Total capitalization............................  $    154      $             $
                                                            ========      ========      ========
------------
(1) For information regarding OneSource's long-term debt and capital lease
    obligations, see Notes 4 and 13 to the Consolidated Financial Statements.
(2) The number of shares of common stock issued and outstanding, pro forma as
    adjusted, excludes as of December 31, 1998, 1,983,852 shares of common stock
    issuable upon the exercise of stock options and warrants outstanding at a
    weighted average exercise price of $2.57, and an aggregate of 252,760 shares
    reserved for future stock option grants and purchases under OneSource's
    equity compensation plans. For more information, see "Management--Equity
    Plans" and Notes 7 and 8 to the Consolidated Financial Statements.
 
                                       16
18
 
                                    DILUTION
 
     The net tangible book value per share of our common stock immediately after
this offering will be substantially less than the initial public offering price
because the assumed initial public offering price is substantially higher than
the current net tangible book value per share. The pro forma net tangible book
value deficit of OneSource as of December 31, 1998 was $(6.3) million, or
$(      ) per share. Pro forma net tangible book value per share represents the
amount of total tangible assets less total liabilities, divided by the number of
shares of common stock outstanding after giving effect to the reclassification
of all shares of Class P common stock into common stock and the issuance of
                shares of common stock to the holders of Class P common stock in
satisfaction of their preference amount. After giving effect to the sale by
OneSource of the                 shares of common stock offered hereby (at an
assumed initial public offering price of $     per share) and the application of
the estimated net proceeds, the pro forma net tangible book value of OneSource
as of December 31, 1998, would have been $           million, or $     per
share. This represents an immediate increase in pro forma net tangible book
value of $     per share to existing stockholders and an immediate "dilution" of
$     per share to investors purchasing common stock in this offering. The
following table illustrates this per share dilution:
Assumed initial public offering price.......................            $
  Pro forma net tangible book value deficit per share as of
     December 31, 1998......................................  $
  Increase per share attributable to new investors..........
                                                              ------
Pro forma net tangible book value per share after this
  offering..................................................
                                                                        -----
Dilution per share to new investors.........................            $
                                                                        =====
The following table summarizes, as of December 31, 1998, the difference
between the number of shares of common stock purchased from OneSource, the total
consideration paid to OneSource, and the average price per share paid by
existing stockholders and by new investors (at an assumed initial public
offering price of $     per share before deduction of the estimated underwriting
discount and offering expenses payable by OneSource):
SHARES PURCHASED        TOTAL CONSIDERATION
                                      ---------------------    ----------------------    AVERAGE PRICE
                                        NUMBER      PERCENT      AMOUNT       PERCENT      PER SHARE
                                      ----------    -------    -----------    -------    -------------
Existing stockholders...............                      %    $                    %       $
New investors.......................                                                        $
                                      ----------     -----     -----------     -----
     Total..........................                 100.0%    $               100.0%
                                      ==========     =====     ===========     =====
The foregoing tables (a) assume the repurchase of         of the shares of
common stock issued in the reclassification and (b) assume no exercise of the
options or the warrants outstanding as of December 31, 1998 to purchase an
additional         shares of common stock at a weighted average exercise price
of $     per share. To the extent these options or warrants are exercised, there
will be further dilution to new shareholders in the net tangible book value of
their shares. For more information, see "Management--Equity Plans." In addition,
the second table does not reflect the sale of         shares by the selling
stockholders in this offering. Such sales will reduce the number of shares held
by existing shareholders as of December 31, 1998 to                 , or
approximately      % of the total shares of common stock to be outstanding after
this offering (     % if the over-allotment option is exercised in full), and
will increase the number of shares to be purchased by the new shareholders to
                or      % (     % if the over-allotment option is exercised in
full) of the total shares of common stock to be outstanding after this offering.
For more information, see "Principal and Selling Stockholders."
 
                                       17
19
 
                      SELECTED CONSOLIDATED FINANCIAL DATA
 
     The selected consolidated financial data set forth below should be read in
conjunction with OneSource's Consolidated Financial Statements and Notes thereto
and "Management's Discussion and Analysis of Financial Condition and Results of
Operations," appearing elsewhere in this prospectus. The consolidated statement
of operations data for the years ended December 31, 1996, 1997 and 1998, and the
consolidated balance sheet data as of December 31, 1997 and 1998, have been
derived from, and are qualified by reference to, OneSource's audited
Consolidated Financial Statements appearing elsewhere in this prospectus. The
consolidated statement of operations data for the years ended December 31, 1994
and 1995, and the consolidated balance sheet data as of December 31, 1994, 1995
and 1996, have been derived from audited Consolidated Financial Statements of
OneSource that do not appear in this prospectus. The historical results are not
necessarily indicative of the operating results to be expected in the future.
YEAR ENDED DECEMBER 31,
                                                ----------------------------------------------------
                                                  1994       1995       1996       1997       1998
                                                --------   --------   --------   --------   --------
                                                  (IN THOUSANDS, EXCEPT SHARE AND PER SHARE DATA)
STATEMENT OF OPERATIONS DATA:
Revenues:(1)
  Web-based product...........................  $     --   $     --   $     15   $  3,312   $ 16,058
  CD Rom product..............................    30,300     28,957     30,419     27,072     14,370
                                                --------   --------   --------   --------   --------
  Total revenues..............................    30,300     28,957     30,434     30,384     30,428
                                                --------   --------   --------   --------   --------
Cost of revenues:
  Web-based product...........................        --         --        295      2,401      7,863
  CD Rom product..............................    12,380     11,520     12,244     10,444      5,792
                                                --------   --------   --------   --------   --------
  Total cost of revenues......................    12,380     11,520     12,539     12,845     13,655
                                                --------   --------   --------   --------   --------
Gross profit..................................    17,920     17,437     17,895     17,539     16,773
                                                --------   --------   --------   --------   --------
Operating expenses:
  Selling and marketing.......................    11,231      8,705      8,572      9,167     11,577
  Platform and product development............     5,512      6,585      7,252      6,375      6,313
  General and administrative..................     6,516      5,163      3,664      3,401      3,847
                                                --------   --------   --------   --------   --------
  Total operating expenses....................    23,259     20,453     19,488     18,943     21,737
                                                --------   --------   --------   --------   --------
Loss from operations..........................    (5,339)    (3,016)    (1,593)    (1,404)    (4,964)
Interest income (expense), net................      (515)      (633)      (733)      (930)      (595)
Gain on sale of product line..................        --         --         --        501     12,797
                                                --------   --------   --------   --------   --------
Income (loss) before income taxes and
  extaordinary gain...........................    (5,854)    (3,649)    (2,326)    (1,833)     7,238
Provision (benefit) for income taxes..........      (473)        --         --         --        250
Extraordinary gain on early extinguishment of
  debt........................................        --         --        393         --         --
                                                --------   --------   --------   --------   --------
Net income (loss).............................    (5,381)    (3,649)    (1,933)    (1,833)     6,988
Less: income (loss) attributable to Class P
  common stock................................      (122)       104        335        414      1,367
                                                --------   --------   --------   --------   --------
Income (loss) attributable to common stock....  $ (5,259)  $ (3,753)  $ (2,268)  $ (2,247)  $  5,621
                                                ========   ========   ========   ========   ========
Earnings (loss) per share:(2)
  Class P common stock:
    Basic and diluted earnings (loss) per
share.........................................  $  (0.34)  $   0.29   $   0.95   $   1.17   $   3.88
    Weighted average Class P common shares
       outstanding............................   355,900    355,400    353,300    352,800    352,600
18
20
YEAR ENDED DECEMBER 31,
                                                ----------------------------------------------------
                                                  1994       1995       1996       1997       1998
                                                --------   --------   --------   --------   --------
Common stock:
    Basic earnings (loss) per share...........  $  (1.64)  $  (1.17)  $  (0.71)  $  (0.70)  $   1.72
    Diluted earnings (loss) per share.........  $  (1.64)  $  (1.17)  $  (0.71)  $  (0.70)  $   1.20
    Weighted average common shares
      outstanding:
       Basic..................................  3,206,431  3,205,223  3,187,695  3,216,385  3,263,309
       Diluted................................  3,206,431  3,205,223  3,187,695  3,216,385  4,699,337
  Unaudited pro forma earnings per share:(3)
    Basic.....................................                                              $
    Diluted...................................                                              $
    Weighted average common shares outstanding
       Basic..................................
       Diluted................................
DECEMBER 31,
                                                ----------------------------------------------------
                                                  1994       1995       1996       1997       1998
                                                --------   --------   --------   --------   --------
                                                   (IN THOUSANDS, EXCEPT NUMBER OF CUSTOMER DATA)
BALANCE SHEET DATA:
Cash and cash equivalents.....................  $  1,378   $    966   $    535   $    341   $  8,665
Working capital (deficit).....................    (7,431)    (7,499)    (8,803)    (9,792)    (2,118)
Total assets..................................    19,396     16,567     16,934     16,644     27,646
Total debt (including capital lease
  obligations)................................     4,755      6,223      6,661      8,171      6,936
Deferred revenues.............................    13,818     14,160     15,419     15,748     18,022
Total stockholders' deficit...................    (6,116)    (9,757)   (11,827)   (13,613)    (6,311)
 
OTHER DATA FOR WEB-BASED PRODUCTS (UNAUDITED):
Annualized contract value(4)..................  $     --   $     --   $    412   $  8,973   $ 25,920
Number of customers...........................        --         --         11        233        445
Average annualized contract value per
  customer....................................  $     --   $     --   $   37.4   $   38.5   $   58.2
------------
(1) In 1997 and 1998, OneSource divested certain CD Rom product lines. Revenues
    attributable to these divested product lines, which are included in the
    statement of operations data through the divestiture date, were $5,713,000,
    $6,002,000, $6,415,000, $6,630,000 and $2,612,000 in the years ended
    December 31, 1994, 1995, 1996, 1997 and 1998, respectively.
 
(2) You should read Notes 2 and 5 to the Consolidated Financial Statements for
    further description of the calculation of these items.
 
(3) Unaudited pro forma basic and diluted earnings per share of common stock for
    the year ended December 31, 1998 have been calculated based on net income
    attributable to all classes of common stock and assuming the
    reclassification of OneSource's Class P common stock prior to the completion
    of this offering as if it had occurred at January 1, 1998. In the
    reclassification, each share of Class P common stock will be reclassified
    into one share of common stock plus an additional number of shares of common
    stock (determined by dividing the preference amount for such share by the
    assumed initial public offering price of $        per share). As described
    in "Use of Proceeds", OneSource intends to use a portion of its net proceeds
    to repay a $6.2 million note due to Lotus Development Corporation and to pay
    $1.0 million to terminate certain management fee arrangements. Accordingly,
    had the note repayment and the management fee termination occurred at
    January 1, 1998, unaudited supplemental pro forma basic and diluted earnings
    per share for the year ended December 31, 1998 would be $        and
    $        , respectively. Such amounts reflect the elimination of annual
    interest expense on the note of $0.5 million and the elimination of annual
    management fees of $0.2 million, and the issuance of             shares of
    common stock at the assumed initial public offering price of $        per
    share necessary to fund the note repayment and management fee termination.
 
(4) Annualized contract value represents the invoiced fees for one month for all
    customer contracts for Web-based products in effect at the measurement date,
    multiplied by 12, without regard to the actual remaining duration of such
    contracts. At December 31, 1996, 1997 and 1998, annualized contract value
    was calculated by multiplying the total amount of fees invoiced for one
    month and included in deferred revenues for all customer contracts for
    Web-based products at December 31, 1996, 1997 and 1998 of $34,300, $747,750
    and $2,160,000, respectively, by 12. For more information regarding
    annualized contract value, see "Management's Discussion and Analysis of
    Financial Condition and Results of Operations."
 
                                       19
21
 
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
OVERVIEW
 
     OneSource provides Web-based business and financial information to
professionals who need quick access to reliable corporate, industry and market
intelligence. OneSource was formed as a division of Lotus in 1987 and became an
independent company when it was purchased in a management buy-out in 1993. Until
December 1996, our business was to provide business information to the financial
community using CD Rom technology as the primary method of distribution. The
introduction of Business Browser in December 1996 marked a fundamental shift in
our business as we began a transition away from our legacy CD Rom business and
toward Web-based products.
 
     Revenues from Web-based products accounted for $16.1 million, or 53% of
total revenues, for the year ended December 31, 1998 up from $3.3 million, or
11% of total revenues, for the year ended December 31, 1997. In the same period,
CD Rom product revenues decreased to $14.4 million, or 47% of total revenues for
the year ended December 31, 1998 from $27.1 million, or 89% of total revenues,
for the year ended December 31, 1997. As of December 31, 1998, 445 organizations
subscribed to our Business Browser product line, and the annualized contract
value for these organizations was $25.9 million.
 
     During this transition period, we utilized the cash flow from our CD Rom
business to fund a portion of the significant expenses incurred to build our
Web-based business. These expenses included (a) platform and product development
expenses to develop and enhance our Web-based products, (b) selling and
marketing expenses to hire and train a Web-based sales force and to retrain a
portion of our CD Rom-based sales force and (c) general and administrative
expenses to build the necessary infrastructure to support our growing Web-based
business. The gross margins on our Web-based business have also been adversely
impacted by certain royalty expenses and other costs of revenues which were
disproportionately high compared to Web-based revenues which were growing from
low initial levels. We believe that our operating margins will improve as we
more effectively leverage our Web-based royalty and infrastructure expenses and
eliminate costs incurred to support our legacy CD Rom products.
 
     In May 1998, we sold our CD-Insurance division to allow us to focus more
completely on our new Web-based product line. We recognized a gain of $12.8
million on this sale during 1998. In addition, in connection with the
disposition, we licensed certain of our CD Rom technology to the acquiror in
exchange for $4.0 million of license fees. These license fees will be paid in
eight equal quarterly installments beginning January 1, 1999 and running through
December 31, 2000 and recognized ratably.
 
     One measure of the performance of our business is "annualized contract
value," a term we use as an indicator of business volume and growth, both in
terms of new customers and upgrades and expansions at existing customers. It is
not an absolute indicator and we cannot guarantee that any annualized contract
value will be ultimately realized as revenues. Annualized contract value
represents the total annualized revenue under all customer contracts for
Web-based products in effect at the measurement date, without regard for the
actual remaining duration of such contracts. We have increased annualized
contract value attributable to Web-based products 189% to $25.9 million as of
December 31, 1998 from $9.0 million as of December 31, 1997. The
 
                                       20
22
 
number of on-line customers has increased 91%, to 445 at December 31, 1998 from
233 at December 31, 1997. At the same time, the average annualized contract
value of all Web-based product customers has increased 51%, to $58,248 per
customer at December 31, 1998 from $38,512 per customer at December 31, 1997.
The average annualized contract value for the customers that were under contract
at both December 31, 1997 and 1998 grew to $76,143 per customer at December 31,
1998 from $38,512 per customer at December 31, 1997. This growth was
attributable to an increase in the number of user seats purchased by customers
and the addition of new products.
 
     The renewal rate of the Business Browser product line for 1998 was 90%
calculated on a dollar basis. The renewal rate is measured by comparing a
customer's annualized contract value at December 31, 1998 to its annualized
contract value at December 31, 1997. The set of customers measured are those who
had subscriptions in effect at December 31, 1997.
 
     Our revenues (for both CD Rom and Web-based products) consist of monthly
subscription fees from customer contracts. Customer contracts span varying
periods of time but are generally for one year, are renewable for like periods,
and are payable in advance. Subscription fees generally are quoted to clients on
an annual basis but are earned as revenues on a monthly basis over the
subscription period. Invoices are recorded as accounts receivable until paid and
as deferred revenues until earned. Deferred revenues attributable to Web-based
products increased 231% to $15.9 million as of December 31, 1998 from $4.8
million as of December 31, 1997.
 
     Cost of revenues consists primarily of royalties to information providers
and, to a lesser extent, employee salaries and related expenses (including
benefits and facilities allocation), depreciation associated with computers for
data processing and on-line requirements and Web hosting expenses. We enter into
contracts with our information providers which are generally for a term of at
least one year and are automatically renewable if not canceled with advance
notice. These contracts may be terminated under certain circumstances. For more
information, see "Risk Factors--We depend entirely on our information providers
for content." Under these arrangements, royalties are generally paid on a
quarterly basis to information providers. Royalties generally are calculated
either as a flat percentage of our revenues or as a per-user fee that declines
as the number of authorized users of the product increases. In limited cases, we
pay a fixed fee per period.
 
     Selling and marketing expense consists primarily of employee salaries and
sales commissions paid to our sales force, customer support organization and
marketing personnel, as well as related expenses (including benefits and
facilities allocation), direct marketing promotional materials, trade show
exhibitions and advertising. Sales commissions are paid when customers are
invoiced and are recorded as deferred subscription costs, which are amortized
ratably over the term of the contract, typically 12 months, as the associated
revenues are recognized. All other selling and marketing costs are expensed as
incurred.
 
     Platform and product development expense consists primarily of employee
salaries and related expenses (including benefits and facilities allocation) as
well as outside contractor expenses, relating to the development of our
"platform" of core software supporting our products and the development of new
products based upon that platform. Platform and product development expense
includes expenses relating to the editorial staff that implements our KeyID
technology to integrate disparate information sources into our Web-based
products.
 
                                       21
23
 
     General and administrative expense consists primarily of employee salaries
and related expenses (including benefits and facilities allocation) associated
with OneSource's management, finance, human resources, management information
systems and administrative groups. In addition, we will incur non-recurring
charges of (a) approximately $0.2 million in moving and related costs in June
1999 due to the relocation of our headquarters from Cambridge to Concord,
Massachusetts and (b) approximately $0.2 million of financial advisory fees. The
quarterly management fees of $25,000 paid to each of William Blair Venture
Partners and an affiliate of Information Partners Capital will cease in exchange
for the payment of a $0.5 million termination fee to each of these parties upon
completion of this offering. For more information, see "Certain Transactions."
 
RESULTS OF OPERATIONS
 
     The following table sets forth, for the periods indicated, the percentage
of total revenues represented by each line item in OneSource's consolidated
statement of operations. We can give no assurance that the indicated trends in
revenues or operating results will continue in the future.
YEAR ENDED DECEMBER 31,
                                                          -------------------------------
                                                          1996         1997         1998
                                                          -----        -----        -----
                                                          (PERCENTAGE OF TOTAL REVENUES)
Revenues:
  Web-based product.....................................    --%          11%          53%
  CD Rom product........................................   100           89           47
                                                           ---          ---         ----
     Total revenues.....................................   100          100          100
                                                           ---          ---         ----
Cost of revenues:
  Web-based product.....................................     1            8           26
  CD Rom product........................................    40           34           19
                                                           ---          ---         ----
     Total cost of revenues.............................    41           42           45
                                                           ---          ---         ----
Gross profit............................................    59           58           55
Operating expenses:
  Selling and marketing.................................    28           30           38
  Platform and product development......................    24           21           21
  General and administrative............................    12           11           12
                                                           ---          ---         ----
Loss from operations....................................    (5)          (4)         (16)
Interest income (expense), net..........................    (2)          (3)          (2)
Gain on sale of product line............................    --            1           42
                                                           ---          ---         ----
Income (loss) before income taxes and extraordinary
  gain..................................................    (7)          (6)          24
Provision for income taxes..............................    --           --            1
Extraordinary gain on early extinguishment of debt......     1           --           --
                                                           ---          ---         ----
Net income (loss).......................................    (6)%         (6)%         23%
                                                           ===          ===         ====
22
24
 
COMPARISON OF RESULTS FOR THE YEARS ENDED DECEMBER 31, 1998 AND 1997
 
     Revenues.  Total revenues remained at approximately the same level of $30.4
million for each of the years ended December 31, 1998 and 1997. Web-based
product revenues increased by 385% to $16.1 million for the year ended December
31, 1998 from $3.3 million for the year ended December 31, 1997. The increase
was attributable to new customers, an increase in the number of user seats
purchased by existing customers and the sale of new products to existing
customers. At the same time, CD Rom product revenues decreased by 47% to $14.4
million in 1998 from $27.1 million in 1997 as OneSource continued its transition
away from its legacy CD Rom business. During this period, CD Rom product
revenues included revenues attributable to our CD-Insurance division which was
sold in May 1998. Revenues from this product line were $2.6 million for the year
ended December 31, 1998 compared to $6.6 million for the year ended December 31,
1997.
 
     Cost of Revenues.  Total cost of revenues increased 6% to $13.7 million for
the year ended December 31, 1998 from $12.8 million for the year ended December
31, 1997. As a percentage of total revenues, total cost of revenues increased to
45% in 1998 from 42% in 1997. The increase in total cost of revenues was
principally due to increased royalty expense for our Web-based products. It was
offset partially by a decrease in our costs of revenues relating to the CD Rom
product line.
 
     Cost of Web-based product revenues increased 227% to $7.9 million for the
year ended December 31, 1998 from $2.4 million for the year ended December 31,
1997. As a percentage of Web-based product revenues, cost of Web-based product
revenues decreased to 49% in 1998 from 72% in 1997, due to an increase in our
customer base. Royalty expense increased as a result of growth in Business
Browser product line revenues and number of user seats sold.
 
     Cost of CD Rom product revenues decreased 45% to $5.8 million for the year
ended December 31, 1998 from $10.4 million for the year ended December 31, 1997.
This decrease was due to decreased revenues reflecting our shift away from the
CD Rom product line. As a percentage of CD Rom product revenues, cost of CD Rom
product revenues increased to 40% in 1998 from 39% in 1997.
 
     Selling and Marketing Expense.  Selling and marketing expense increased 26%
to $11.6 million for the year ended December 31, 1998 from $9.2 million for the
year ended December 31, 1997 principally due to increased expenses incurred to
hire new sales personnel and to train new and existing personnel in connection
with our transition to our new Business Browser product line. Selling and
marketing expense increased as a percentage of total revenues to 38% in 1998
from 30% in 1997.
 
     Platform and Product Development Expense.  Platform and product development
expense decreased 1% to $6.3 million for the year ended December 31, 1998 from
$6.4 million for the year ended December 31, 1997, although as a percentage of
total revenues it remained constant at 21%. The decrease was due principally to
the decrease in salary expense resulting from the elimination of CD-Insurance
product development staff in May 1998 upon the sale of that division and the
elimination of several CD Rom product management positions. This decrease in
salary expense was offset by increased headcount in the Global Strategic Web
Applications Team to meet new product demands.
 
                                       23
25
 
     General and Administrative Expense.  General and administrative expense
increased 13% to $3.8 million for the year ended December 31, 1998 from $3.4
million for the year ended December 31, 1997 principally due to increased
headcount in management information systems and human resources for
infrastructure required to accommodate the growth in our business. General and
administrative expense increased as a percentage of total revenues to 12% in
1998 from 11% in 1997.
 
     Interest Expense, Net.  Interest expense, net of interest income, decreased
36% to $0.6 million for the year ended December 31, 1998 from $0.9 million for
the year ended December 31, 1997 due to an increase in interest income related
to invested cash balances from the sale of the CD-Insurance product line in May
1998.
 
     Gain on Sale of Product Line.  As a result of the sale of the CD-Insurance
division, we recorded a gain of $12.8 million. This gain reflects cash proceeds
received of $11.0 million together with recognition of deferred revenues of $3.1
million and $0.6 million of deferred subscription costs due to the transfer of
related service obligations, net of transaction related expenses.
 
     Income Taxes.  The income tax provision for the year ended December 31,
1998 was $0.3 million and is directly related to the gain on the sale of the
CD-Insurance division. Although the gain on the sale created significant taxable
income for 1998, such gain was largely offset by utilizing our net operating
loss carryforwards.
 
COMPARISON OF RESULTS FOR THE YEARS ENDED DECEMBER 31, 1997 AND 1996
 
     Revenues.  Revenues remained at approximately the same level of $30.4
million for each of the years ended December 31, 1997 and 1996. Web-based
product revenues increased to $3.3 million for the year ended December 31, 1997
from $15,000 for the year ended December 31, 1996 due to the addition of new
customers. At the same time, CD Rom product revenues decreased by 11% to $27.1
million in 1997 from $30.4 million in 1996 as we began our transition to
Web-based products.
 
     Cost of Revenues.  Total cost of revenues increased 2% to $12.8 million for
the year ended December 31, 1997 from $12.5 million for the year ended December
31, 1996. As a percentage of total revenues, total cost of revenues increased
marginally to 42% in 1997 from 41% in 1996. This increase in total cost of
revenues was due principally to increased royalty expense for our Web-based
products. It was partially offset by a decrease in our costs of revenues
relating to the CD Rom product line.
 
     Cost of Web-based product revenues increased to $2.4 million for the year
ended December 31, 1997 from $0.3 million for the year ended December 31, 1996
due to a substantial increase in Web-based customers and related royalty
expenses. Cost of CD Rom product revenues decreased 15% to $10.4 million for the
year ended December 31, 1997 from $12.2 million for the year ended December 31,
1996. This decrease reflected our shift away from the CD Rom product line. As a
percentage of CD Rom product revenues, cost of CD Rom product revenues decreased
to 39% in 1997 from 40% in 1996.
 
     Selling and Marketing Expense.  Selling and marketing expense increased 7%
to $9.2 million for the year ended December 31, 1997 from $8.6 million for the
year ended December 31, 1996 principally due to increased headcount and related
expenses. Total selling
 
                                       24
26
 
and marketing expense increased as a percentage of total revenues to 30% in 1997
from 28% in 1996.
 
     Platform and Product Development Expense.  Platform and product development
expense decreased 12% to $6.4 million for the year ended December 31, 1997 from
$7.3 million for the year ended December 31, 1996 principally due to the
decrease in headcount and related expenses, as well as lower contractor expense.
The reduction in headcount was exclusively in the platform development
organization as we ceased all development efforts related to the CD Rom platform
in 1997 and shifted all resources to Web-based platform and product development.
Platform and product development expense decreased as a percentage of total
revenues to 21% in 1997 from 24% in 1996.
 
     General and Administrative Expense.  General and administrative expense
decreased 7% to $3.4 million for the year ended December 31, 1997 from $3.7
million for the year ended December 31, 1996 principally due to the decrease in
amortization expense of intangibles. The amortization of $9.9 million of
intangibles, originally recorded in 1993 at the time of the management buy-out
of OneSource from Lotus, ended in 1997 with expense of $25,000 compared to $0.7
million in 1996. Increased salary and related expense, resulting from increased
headcount for infrastructure required to meet demands in management information
systems, contracting and UK finance management, partially offset the decrease in
amortization. General and administrative expense decreased as a percentage of
total revenues to 11% in 1997 from 12% in 1996.
 
     Interest Expense, Net.  Interest expense, net of interest income, increased
27% to $0.9 million for the year ended December 31, 1997 from $0.7 million for
the year ended December 31, 1996 due to increased borrowings for working capital
requirements in 1997.
 
     Gain on Sale of Product Line.  In June 1997, we sold our CD-Banking product
line for $0.7 million. As a result of the sale, we recorded a gain of $0.5
million which is net of transaction related expenses.
 
                                       25
27
 
QUARTERLY RESULTS OF OPERATIONS AND OTHER DATA
 
     The following tables set forth a summary of OneSource's unaudited quarterly
operating results for each of the eight quarters in the two-year period ended
December 31, 1998. This information has been derived from unaudited interim
consolidated financial statements that, in the opinion of management, have been
prepared on a basis consistent with the Consolidated Financial Statements
appearing elsewhere in this prospectus and include all adjustments, consisting
of only normal recurring adjustments, necessary for a fair statement of such
information when read in conjunction with OneSource's Consolidated Financial
Statements and Notes thereto. Our operating results and other data for any
quarter are not necessarily indicative of results for any future period.
QUARTER ENDED
                                     ---------------------------------------------------------------------------------------
                                                        1997                                         1998
                                     ------------------------------------------   ------------------------------------------
                                     MAR. 31,   JUNE 30,   SEPT. 30,   DEC. 31,   MAR. 31,   JUNE 30,   SEPT. 30,   DEC. 31,
                                     --------   --------   ---------   --------   --------   --------   ---------   --------
                                                                         (IN THOUSANDS)
STATEMENT OF OPERATIONS DATA (UNAUDITED):
Revenues:
  Web-based product................   $  172     $  369     $  979      $1,792    $ 2,628    $ 3,419     $ 4,479    $ 5,532
  CD Rom product...................    7,348      7,383      6,309       6,032      5,322      4,273       2,725      2,050
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total revenues.....................    7,520      7,752      7,288       7,824      7,950      7,692       7,204      7,582
                                      ------     ------     ------      ------    -------    -------     -------    -------
Cost of revenues:
  Web-based product................      340        451        718         892      1,287      1,872       2,070      2,634
  CD Rom product...................    2,769      2,747      2,523       2,405      1,979      1,643       1,159      1,011
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total cost of revenues.............    3,109      3,198      3,241       3,297      3,266      3,515       3,229      3,645
                                      ------     ------     ------      ------    -------    -------     -------    -------
Gross profit.......................    4,411      4,554      4,047       4,527      4,684      4,177       3,975      3,937
                                      ------     ------     ------      ------    -------    -------     -------    -------
Operating expenses:
  Selling and marketing............    2,168      2,195      2,346       2,458      2,797      2,904       2,861      3,015
  Platform and product
    development....................    1,544      1,745      1,608       1,478      1,561      1,528       1,638      1,586
  General and administrative.......      929        749        686       1,037        957      1,051         897        942
                                      ------     ------     ------      ------    -------    -------     -------    -------
    Total operating expenses.......    4,641      4,689      4,640       4,973      5,315      5,483       5,396      5,543
                                      ------     ------     ------      ------    -------    -------     -------    -------
Loss from operations...............   $ (230)    $ (135)    $ (593)     $ (446)   $  (631)   $(1,306)    $(1,421)   $(1,606)
                                      ======     ======     ======      ======    =======    =======     =======    =======

                                                                 (PERCENTAGE OF TOTAL REVENUES)
Revenues:
  Web-based product................        2%         5%        13%         23%        33%        44%         62%        73%
  CD Rom product...................       98         95         87          77         67         56          38         27
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total revenues.....................      100        100        100         100        100        100         100        100
                                      ------     ------     ------      ------    -------    -------     -------    -------
Cost of revenues:
  Web-based product................        4          6         10          11         16         24          29         35
  CD Rom product...................       37         35         35          31         25         22          16         13
                                      ------     ------     ------      ------    -------    -------     -------    -------
Total cost of revenues.............       41         41         45          42         41         46          45         48
                                      ------     ------     ------      ------    -------    -------     -------    -------
Gross profit.......................       59         59         55          58         59         54          55         52
                                      ------     ------     ------      ------    -------    -------     -------    -------
Operating expenses:
  Selling and marketing............       29         28         32          32         35         38          40         40
  Platform and product
    development....................       21         23         22          19         20         20          23         21
  General and administrative.......       12         10          9          13         12         13          12         12
                                      ------     ------     ------      ------    -------    -------     -------    -------
    Total operating expenses.......       62         61         63          64         67         71          75         73
                                      ------     ------     ------      ------    -------    -------     -------    -------
Loss from operations...............       (3)%       (2)%       (8)%        (6)%       (8)%      (17)%       (20)%      (21)%
                                      ======     ======     ======      ======    =======    =======     =======    =======
 
OTHER DATA FOR WEB-BASED PRODUCTS
  (AS OF THE QUARTER END)
  (UNAUDITED):                                           (IN THOUSANDS, EXCEPT NUMBER OF CUSTOMERS DATA)
Annualized contract value..........   $  981     $2,430     $4,815      $8,973    $11,854    $14,619     $19,754    $25,920
Number of customers................       37         92        149         233        279        322         386        445
Average annualized contract value
  per customer.....................   $ 26.5     $ 26.4     $ 32.3      $ 38.5    $  42.5    $  45.4     $  51.2    $  58.2
26
28
 
     Annualized contract value represents the invoiced fees for one month for
all customer contracts for Web-based products in effect at the measurement date,
multiplied by 12, without regard to the actual duration of such contracts. At
March 31, June 30, September 30 and December 31, 1997 and March 31, June 30,
September 30 and December 31, 1998, annualized contract value was calculated by
multiplying the total amount of fees invoiced for one month and included in
deferred revenues for all customer contracts for Web-based products at March 31,
June 30, September 30 and December 31, 1997 and March 31, June 30, September 30
and December 31, 1998 of $81,750, $202,500, $401,250 and $747,750 and $987,850,
$1,218,250, $1,646,200 and $2,160,000, respectively, by 12.
 
     Our quarterly revenues, gross profits and results of operations have
fluctuated significantly in the past and we expect them to continue to fluctuate
significantly in the future. In addition, we believe that an important measure
of our business is the annualized contract value at the end of each period,
which also may fluctuate. Causes of such fluctuations have included and may
include, among other factors:
 
        - changes in demand for our products
 
        - the dollar value and timing of both new and renewal subscriptions
 
        - competition (particularly price competition)
 
        - changes in operating expenses
 
        - technical difficulties or system downtime affecting our products on
          the Web generally
 
        - economic conditions specific to the Web, as well as general economic
          conditions
 
        - consolidation of our customers
 
In addition, a substantial portion of our expenses, including certain product
development and selling and marketing expenses, must be incurred in advance of
revenue generation. If our projected revenue does not meet our expectations,
then we may have an operating loss in a particular quarter.
 
     Annualized contract value depends upon the timely renewal, upgrade and sale
to new customers of subscription agreements within a quarter and can be
difficult to forecast accurately. In addition, we have experienced some
quarterly seasonality in contract bookings with a significant amount of activity
occurring in the fourth quarter of a given year. Accordingly, these timing
variations can create shortfalls in revenues in relation to our expectations and
have an adverse effect on our operating results.
 
LIQUIDITY AND CAPITAL RESOURCES
 
     Since acquiring our business from Lotus in 1993, we have funded our
operations through a combination of seller financing, proceeds received from the
sale of Class P common stock and common stock in connection with the purchase of
the business from Lotus, bank debt, proceeds received from the sale of
non-strategic lines of business, capitalized equipment leases and cash flows
from operations.
 
     Our cash and cash equivalents totaled $8.7 million at December 31, 1998, as
compared to $0.3 million at December 31, 1997, an increase of $8.3 million. Net
cash of $1.2 million was provided by operations for the year ended December 31,
1998, primarily resulting from growth in contracts invoiced for the period. Net
cash provided by investing activities for 1998 was $9.0
 
                                       27
29
 
million, primarily reflecting net cash proceeds from the sale of the
CD-Insurance division, offset partially by expenditures of $1.3 million for
property and equipment. Net cash used in financing activities for the year ended
December 31, 1998 was $2.0 million reflecting primarily repayments on our line
of credit, term loan and capital lease obligations.
 
     We do not currently have a line of credit but intend to enter into a
revolving line of credit for letters of credit and general working capital.
 
     We have a note outstanding to Lotus and the principal amount outstanding at
December 31, 1998 was $6.2 million. This note plus accrued interest is due
September 8, 2000 and a repayment of a portion of the note would be required
upon completion of this offering. We intend to repay the note upon the
completion of this offering. Upon repayment of the note, the company will
recognize a one-time expense of $        relating to the unamortized portion of
the original issue discount.
 
     We currently anticipate capital expenditures of approximately $2.8 million
for 1999, including approximately $0.9 million in connection with the relocation
of our corporate headquarters, which is scheduled to occur in June 1999.
 
     We expect to investigate the possibility of investing in or acquiring
complementary businesses, products or technologies, although we have not entered
into any commitments or negotiations with respect to any such transactions.
 
     We believe that our net proceeds from this offering, together with our
current cash and cash equivalents and funds anticipated to be generated from
operations, will be sufficient to satisfy working capital and capital
expenditure requirements for at least the next twelve months.
 
YEAR 2000 READINESS DISCLOSURE STATEMENT
 
     We have established a Year 2000 compliance program and we anticipate that
our products and internal systems should operate correctly at the turn of the
century. We have been performing Year 2000 tests for the past three years.
Initial Year 2000 work was organized in late 1996 to certify readiness of the
proprietary client software associated with our CD Rom product line. A more
formal organizational effort involving senior management, product managers,
developers and quality assurance personnel was established in early 1998.
 
     Compliance Program.  The scope of OneSource's compliance program focuses on
four key areas: products, third-party information providers, third-party
software applications and internal systems. Our compliance program involves a
three-step process to evaluate each of the key areas, which includes (a)
inventory review, (b) assessment/testing and (c) resolution and contingency
planning.
 
     Products.  We have assessed existing products to review OneSource's overall
compliance status. We have decided not to test those products that will be
discontinued prior to December 31, 1999. This includes, for example, all
products associated with our CD Rom product line with the exception of the "UK
Companies" product, which we expect to produce beyond 1999. We have established
clear migration paths for those customers who have products installed that will
be discontinued. As of February 1999, we had completed almost all work
associated with creating internal company awareness of Year 2000 issues,
organizing and executing high-level plans to address the concern, and
inventorying existing systems, data, and software dependency for Year 2000
exposure. We estimate that as of February 1999 we had
 
                                       28
30
 
completed about two-thirds of the process of analyzing the impact of Year 2000
issues company-wide and developing detailed plans for resolving problem
situations. We are in the midst of implementing those plans. Resolution of
outstanding Year 2000 issues for non-Information Services applications are being
incorporated with plans to move our corporate offices in June 1999. Projects
that involve IS-related issues (particularly those processes that prepare and
deliver data in our products) are expected to be completed in April 1999, with
follow-up testing, if required, extending through July 1999. In terms of
verifying and planning for Year 2000 compliance for our products, we use the
British Standards Institute's definition of Year 2000 compliance as stated in
DISC PD2000-1:1998: A Definition of Year 2000 Conformity Requirements. According
to this definition, Year 2000 conformity means that neither performance nor
functionality is affected by dates prior to, during and after the year 2000, and
according to the following rules:
 
        - No value for current date will cause any interruption in operation
 
        - Date-based functionality must behave consistently for dates prior to,
          during and after the year 2000
 
        - In all interfaces and data storage, the century in any date must be
          specified either explicitly or by unambiguous algorithms or
          inferencing rules
 
        - Year 2000 must be recognized as a leap year
 
     New products under development for this year and next have Year 2000
qualification as part of their standard test plans. Products that fail their
standard test plans are not released to customers.
 
     Third-Party Information Providers.  OneSource relies on content provided by
third-party information providers. Communication with our information providers
with respect to their Year 2000 compliance status was largely complete as of
February 1999. OneSource's goal is to have all information providers' compliance
responses complete by March 31, 1999. We are also trying to minimize our
dependence on third-party information providers' external date formats by
accommodating changes in date format within our existing production processes.
 
     Third-Party Application and System Software.  OneSource invests in
third-party software as components of the data storage and delivery requirements
of our products. We have identified an exhaustive list of such systems along
with research of the current status of their Year 2000 compliance efforts. We
completed this research in February 1999. Our goal is to have confirmation of
compliance or a specific plan to replace any non-compliant resource by March 31,
1999. Only a short list of these resources remains non-compliant as of February
1999. While OneSource is committed to taking every reasonable action to obtain
assurances from such business partners that their software is Year 2000
compliant, we cannot guarantee the performance of such business partners or
predict whether any of the assurances provided by them may be accurate or
realistic.
 
     Internal Systems.  OneSource has completed its inventory of its internal
systems and its assessment of such systems' compliance status is approximately
50% complete, with an anticipated completion date of March 31, 1999. The scope
of these systems ranges from accounting, payroll, communications, network
hardware and applications, Internet access, internal information systems and
data production systems. The majority of our internal systems and equipment are
currently Year 2000 compliant. Some existing Year 2000 issues (e.g.,
 
                                       29
31
 
OneSource's phone switch and some components of the Corporate Local Area
Network) will be addressed as part of the relocation of our offices in June
1999.
 
     Costs.  To date we have not relied on outside consulting expertise for
assessing our products or testing for Year 2000 related issues. We are utilizing
internal personnel to identify Year 2000 readiness in our supported products,
network hardware/applications, internal business and information systems. A
large number of our personnel are necessarily involved in this work. We estimate
that the aggregation of all such efforts represents an equivalent of six
full-time employees (efforts at this level dating back approximately one year).
Not included in this estimate are those indirect costs associated with time
spent by management or staff discussing Year 2000 issues internally or with
third parties. Such discussions are handled by existing employees in the
ordinary course of business. We have not identified the need to hire additional
staff specifically to address third-party questions or concerns.
 
     Risks.  With regard to third-party information suppliers, OneSource is
addressing, through normal operating procedures any concerns that third-party
information providers may have delivery problems associated with Year 2000
issues. OneSource is identifying issues by internal quality assurance or
editorial reviewers. When identified, issues are being handled by contacting the
information provider who may correct the problem at the source or by developing
a workaround in the software. The risks associated with delivery problems
present more serious issues for us as our products could be deprived of certain
data content.
 
     While OneSource does not anticipate a failure in its ability to deliver
data, and has established contingency plans as discussed below, such a failure
may (a) have a material adverse effect upon our business, financial condition
and results of operations, (b) require us to incur unanticipated material
expenses to remedy any problem and (c) result in litigation due to our inability
to fulfill our contractual obligations. In such cases, we would likely suffer a
disruption in our revenue stream and operations could be materially impacted.
 
     Contingency Plans.  At this time, our contingency plans relating to the
above discussed Year 2000 issues include having additional support staff and
programmers on call for rapid response dealing with any disruption of our
business during a critical date transition (e.g., January 1, 2000, February 29,
2000). Our assessment of our products and internal systems for Year 2000
compliance will be an ongoing effort throughout the remainder of this year. The
information contained herein is the product of conclusions made from the
information and test results available to OneSource at this time.
 
RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS
 
     In March 1998, the Accounting Standards Executive Committee ("AcSEC")
issued Statement of Position ("SOP") 98-1, "Accounting for the Costs of Computer
Software Developed or Obtained for Internal Use." SOP 98-1 establishes the
accounting for costs of software products developed or purchased for internal
use, including when such costs should be capitalized. We do not expect SOP 98-1,
which is effective for OneSource beginning January 1, 1999, to have a material
effect on our financial condition or results of operations.
 
     In April 1998, the AcSEC issued SOP 98-5, "Reporting on the Costs of
Start-Up Activities." Start-up activities are defined broadly as those one-time
activities relating to opening a new facility, introducing a new product or
service, conducting business in a new territory,
 
                                       30
32
 
conducting business with a new class of customer, commencing some new operation
or organizing a new entity. Under SOP 98-5, the cost of start-up activities
should be expensed as incurred. SOP 98-5 is effective for OneSource's calendar
year 1999 financial statements and we do not expect its adoption to have a
material effect on our financial condition or results of operations.
 
     In June 1998, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards ("SFAS") No. 133, "Accounting for Derivative
Instruments and Hedging Activities." The new standard establishes accounting and
reporting standards for derivative instruments, including certain derivative
instruments embedded in other contracts, and for hedging activities. SFAS No.
133 is effective for all fiscal quarters of fiscal years beginning after June
15, 1999. We do not expect SFAS No. 133 to have a material effect on our
financial condition or results of operations.
 
                                       31
33
 
                                    BUSINESS
 
     This prospectus contains certain forward-looking statements that involve
substantial risks and uncertainties. Our actual results, performance or
achievements could differ materially from the results expressed in or implied by
these forward-looking statements. Factors that could cause or contribute to such
differences include those discussed in "Risk Factors."
 
OVERVIEW
 
     OneSource provides Web-based business and financial information to
professionals who need quick access to reliable corporate, industry and market
intelligence. Our Business Browser product line integrates comprehensive and
up-to-date business and financial information on over one million public and
private companies from more than 25 information providers drawing upon over
2,500 sources of content. These sources include both textual information, such
as news, trade press, SEC filings, executive biographies and analyst reports,
and numeric information, such as company financial results, stock quotes and
industry statistics. Our customers access this information over the Internet
using standard Web browsers at a fixed annual subscription price.
 
     Our products are designed to address information needs of leading
professional and financial services firms, technology companies and other large
organizations. Representative customers include American Express, Bain &
Company, BankAmerica, Boeing, British Telecom, Deloitte & Touche, Ernst & Young,
Harvard Business School, KPMG Peat Marwick, MCI/Worldcom, Merrill Lynch, Oracle
and SAP.
 
     At December 31, 1998, 445 organizations subscribed to our Web-based
Business Browser product line, up from 233 at December 31, 1997. On average, our
customers for Web-based products at December 31, 1998 had an annualized contract
value of $58,248 per customer, compared to $38,512 per customer at December 31,
1997. The annualized value of Business Browser customer contracts was $25.9
million at December 31, 1998, having grown from $9.0 million at the end of 1997.
Of this $25.9 million, $14.2 million was attributable to those customers that
were under contract at both December 31, 1997 and 1998. The renewal rate of the
Business Browser product line for 1998 was 90% calculated on a dollar basis.
 
INDUSTRY BACKGROUND
 
     According to an industry source, the market for all Web-based and on-line
business information services was $24.8 billion in 1997 and is projected to grow
to $39.8 billion in 2002, reflecting a compound annual growth rate of 9.9%.
According to this industry source, the primary market segment in which OneSource
participates--Web-based and on-line financial news, current awareness and
research services--was $5.4 billion in 1997 and is projected to grow to $9.8
billion in 2002, reflecting a compound annual growth rate of 12.6%.
 
     Recent industry growth has been driven by corporations and other
enterprises recognizing that productivity and competitiveness depend on
extensive knowledge of external information, including information about
industries, customers, competitors, prospects, business trends, breaking news
and market data. These organizations have already invested heavily in Internet
connectivity and networked computing infrastructures to manage internal
information and are seeking to leverage these infrastructures to access and
manage external information.
 
                                       32
34
 
     The task of finding and using external information is often difficult and
cumbersome. Traditional, textual sources such as newspapers and directories
require hours to search. A centralized library can be costly to establish and
maintain and can be an inefficient and incomplete information source. While the
emergence of the Web has greatly increased access to information, finding
comprehensive, precise, up-to-date, relevant and reliable information on the Web
can still be time-consuming and difficult. While other on-line services can be
useful research tools in certain circumstances, most of these services currently
focus on specific areas of content, such as financial data or news. They do not
provide the full range of data required by professionals. In addition, most
on-line services charge a fee for each search performed.
 
     Traditional sources, the Web and existing on-line services do not
adequately meet the information needs of many professionals who want to compete
effectively in today's fast-paced, global, customer-focused marketplace. These
professionals and their organizations demand external information that is:
 
        - easily accessible in a user-friendly format
 
        - comprehensive and includes both textual and numeric information
 
        - derived from multiple, high quality sources
 
        - integrated at a single site
 
        - delivered on a platform that allows interpretation, manipulation and
          analysis
 
        - available throughout the enterprise at a fixed cost
 
        - delivered in a product easily implemented and supported on a corporate
          network
 
THE ONESOURCE SOLUTION
 
     OneSource's Business Browser product line is designed to be a comprehensive
and easy to use business and financial information resource for professionals
who need quick access to reliable corporate, industry and market intelligence.
 
     Business Browser products integrate over 2,500 sources of business
information from more than 25 category-leading business and financial
information providers. These sources include both textual information, such as
news, trade press, SEC filings, executive biographies and analyst reports, and
numeric information, such as company financial results, stock quotes and
industry statistics. OneSource uses its proprietary KeyID technology to sort,
prioritize, integrate and link information on over one million public and
private companies worldwide.
 
     Our Business Browser product line is accessed through a standard Web
browser that is already available and familiar to end-users. Because our
products are based on standard Web technology, our customers require minimal
installation and systems support and users have full access to the products at
any time from anywhere via the Internet.
 
     OneSource focuses on the functional uses of the business and financial
information it delivers. The Business Browser product line has been designed for
use not only by traditional users of business information, but also throughout
an organization, including sales, marketing, finance and management
professionals. We apply our knowledge of how business professionals use
information to transform raw, disparate data into meaningful, actionable
information. We focus on integrating and presenting information so that
interpretation, manipulation and analysis
 
                                       33
35
 
can be performed more easily by the end user. Because the interface is built
around the inquiries of professionals, users require minimal training to become
productive quickly.
 
     OneSource's pricing strategy is designed to be particularly attractive to
large organizations. The Business Browser product line is available at a fixed
annual subscription price which declines on a per-user basis as the total number
of users increases for that customer. The fixed-price model encourages
professionals to use the products as needed without concern with additional
charges, and a declining marginal price per user encourages customers to
distribute our products widely throughout their organizations.
 
STRATEGY
 
     Our goal is to become a leading Web-based provider of business and
financial information to professionals worldwide. To accomplish that goal, we
have adopted the following strategies:
 
     --Focus on Information Needs of Professionals in Large Organizations.  We
believe that professional and financial services firms, technology companies and
other large organizations have the widely distributed Web access necessary to
take advantage of the Business Browser product line and are most likely to be
willing to purchase external information services to gain the competitive
advantages available through our products. While many alternative products are
focused on small organizations and individual consumers, our product and pricing
strategies and sales and marketing efforts have been designed to address the
needs of large enterprises.
 
     --Expand Customer Base.  At December 31, 1998, 445 organizations subscribed
to our Web-based Business Browser product line, up from 233 at December 31,
1997. One group of our direct sales force, our account executives, concentrates
primarily on selling the Business Browser product line to new customers. We
intend to continue to invest in training our sales force and in recruiting
technically qualified sales personnel to sell Business Browser products. In
addition, while the traditional users of on-line business information services
have been primarily financial analysts and professional service providers, we
have expanded our target customer base to include corporations which are
purchasing our products for use by their sales, marketing, finance and
management professionals. We also intend to explore selective third-party
distribution of our products primarily to expand geographic coverage. For
example, we recently entered into an agreement with Dun & Bradstreet under which
they will serve as a distributor of our European Business Browser product.
 
     --Leverage Existing Customer Base.  We will continue to seek to increase
sales to existing customers by expanding the number of authorized user seats at
each customer and by upgrading customers to new products, more extensive content
and increased functionality. Each customer is assigned an account manager who is
responsible for that customer's retention, monitoring that customer's needs and
assisting that customer with rollouts and upgrades. The average annualized
contract value at December 31, 1998 of Business Browser customers who were also
customers at December 31, 1997 was $76,143 per customer, compared to $38,512 per
customer at December 31, 1997, an increase of 98% during the course of the year.
 
     --Expand Content and Product Offerings.  Since introducing Business Browser
in December 1996, we have followed a strategy of enhancing the Business Browser
product line by adding content from new sources, increasing functionality and
designing products tailored to particular markets. For example, in January 1999
we introduced European Business Browser, which includes content focused on the
European market, and in December 1998 we introduced
 
                                       34
36
 
AppLink, which permits customers to integrate content from Business Browser
products within the customer's own intranet applications, such as sales force
automation applications.
 
     --Strategic Alliances and Possible Acquisitions.  We will seek to expand
our distribution channels in part by seeking strategic alliances with partners,
such as vendors of sales automation software, who may use AppLink to integrate
content from the Business Browser products into their software offerings. In
addition, OneSource may seek additional content sources, distribution channels
or technology through selective acquisitions or strategic alliances, although we
are not currently in discussions regarding any potential acquisitions or
alliances.
 
PRODUCTS
 
  Business Browser Product Line
 
     The Business Browser product line includes:
 
     US BUSINESS BROWSER.  Released in December 1996, US Business Browser is
focused specifically on the US and Canada. It contains a subset of business and
financial information from the Global Business Browser product. It covers over
250,000 public and private companies in the US and Canada.
 
     UK BUSINESS BROWSER.  Released in September 1997, UK Business Browser is a
comprehensive source of information on over 350,000 public and private companies
in the UK.
 
     GLOBAL BUSINESS BROWSER.  Released in December 1997, Global Business
Browser is a single, integrated resource that provides information on over
350,000 public and private companies from around the world.
 
     EUROPEAN BUSINESS BROWSER.  Released in January 1999, European Business
Browser provides users with a comprehensive database on 300,000 public and
private companies across Europe, including 50,000 UK companies. An important
source of data for the European Business Browser is Dun & Bradstreet, a leading
business information source.
 
     Business Browser delivers information in an integrated format. This allows
customers to obtain different types of information from multiple sources in a
single report. Business Browser products organize data around business
applications and transform raw, disparate data into meaningful, actionable
information, delivered according to the characteristics users have defined and
in the custom formats, tables and reports that users require. Users who need to
perform detailed analysis can also easily transfer quantitative data into
spreadsheets or other desktop tools, such as contact management software.
 
     Specific applications available through the Business Browser product line
include:
 
        - "Company Profiler" delivers integrated reports on a company's history,
          products, competition, industry, executives, current news articles and
          financials. Both summary and detailed company reports are available,
          depending on the user's need. In addition, "Corporate Family Reports"
          allow users to quickly map relationships among subsidiaries and
          divisions of corporations.
 
        - "WatchList Update" automatically keeps track of new articles, news
          stories, financial filings and research reports on the companies the
          user monitors.
 
        - "Industry Profiler" delivers reports on market size, segmentation,
          financial norms, ratios and forecasts for a specified industry, as
          well as participants, industry news and
 
                                       35
37
 
          analysis, and creates research reports with graphs and statistics that
          help track industry trends.
 
        - "Company Finder" screens companies by defining key search
          characteristics to deliver a targeted list by industry, geography,
          size, revenues, employment or other key characteristics.
 
        - "Topic Search" screens news stories, research reports, business
          descriptions and trade articles for information by topic.
 
        - "Executive Search" provides users with reports on business leaders by
          name, company, location, schools and affiliated organizations.
 
  Additional Software Applications
 
     Two additional software applications are available with Business Browser
products.
 
     BUSINESS BROWSER AP.  Business Browser AP, which became commercially
available in August 1997, is an advanced Web-based quantitative analysis tool
available as an option with all of the Business Browser products other than
European Business Browser. Business Browser AP lets users screen across a wide
range of public company financial statement items, ratios, growth rates and
other criteria. It also allows users to produce detailed quantitative reports of
their own design. Business Browser AP also makes EDGAR documents more user
friendly by removing confusing computer codes, formatting tables for easy
viewing and printing, and allowing users to export tables to a spreadsheet.
 
     BUSINESS BROWSER APPLINK.  Business Browser AppLink, which became
commercially available in December 1998, is a software toolkit that allows
customers to easily incorporate Business Browser content (e.g., company
profiles, news, business and trade articles, analyst reports, executive
biographies, industry intelligence and financial data) directly into corporate
intranet applications. Users have the ability to integrate in-depth, objective
external business information into their existing internal applications such as
prospect and customer databases, sales force automation tools, enterprise
reporting software and corporate Web applications. No special client software or
dedicated servers are necessary. AppLink-enabled applications are currently
under development at a number of client sites.
 
  Legacy CD Rom Products
 
     Prior to our introduction of Business Browser in 1996, we distributed
business information on CD Rom. Having made the strategic decision to transition
to a completely Web-based business, we began in 1998 to phase out our CD Rom
products. We expect that all but two of these products will be completely phased
out by the end of 1999, with the remaining two products being phased out shortly
thereafter.
 
PLATFORM AND PRODUCT DEVELOPMENT
 
     The product development function is currently carried out by 38 employees
in our Global Strategic Web Applications Team. This team includes product
managers who define functional software components, end user interfaces, report
formats and content requirements; product development engineers who take content
feeds from information partners and write database loader code; and the KeyID
team whose role, through both programming and editorial expertise,
 
                                       36
38
 
is to ensure consistent integration and presentation of information from
multiple underlying sources of content.
 
     Our product development strategy is to deliver a broad range of information
on a software platform which allows end users to efficiently research their
business questions. Since the inception of the Business Browser product line, we
have consistently added sources of content and improved the software
functionality for users. In the future, we expect to continue to make these
types of improvements to our product line.
 
     The product development team uses our proprietary KeyID technology to
integrate and link public and private companies worldwide from multiple
databases, each with its own set of incompatible identifiers. Through a
combination of proprietary programmatic and editorial means, this technology
enables us to provide a single and unified presentation from multiple underlying
company databases. It also manages multiple SIC codes and industry mappings
assigned to companies by disparate databases and reclassifies the companies to
comparable categories. The system also keeps track of company name synonyms to
allow searching by commonly used alternative company names. The synonyms feature
allows the user to input one company name or term and to access all information
for that company although it may be categorized under different names or terms
depending on the database. In total, the KeyID database contains 1.1 million
companies, 1.7 million synonyms and 40,000 URLS.
 
                                       37
39
 
INFORMATION PROVIDERS
 
     Each Business Browser product combines an array of carefully chosen
financial, company, industry, executive and news-related content obtained from
leading business and financial information providers identified by our Global
Strategic Web Applications Team. The following table lists the type of content
provided by our current information providers and which Business Browser
products include that content.
BUSINESS BROWSER PRODUCT
                                                                    -------------------------
      TYPE OF INFORMATION              INFORMATION PROVIDER         GLOBAL   US    UK    EURO
      -------------------              --------------------         ------   ---   ---   ----
Company Information............  CorpTech                             X       X
                                 Dun & Bradstreet                                         X
                                 Extel (Primark)                      X
                                 Graham & Whiteside Limited           X
                                 Hemmington Scott                                   X
                                 Hoover's Inc.                        X       X
                                 ICC                                                X
                                 InfoUSA                              X       X
                                 Market Guide                         X       X
                                 Reed Elsevier                        X       X
                                 Worldscope (Disclosure Inc.)         X
Industry Reports and Data......  McGraw-Hill                          X       X
                                 Integra                              X       X
                                 The Gale Group                       X       X
                                 Snapshots Intl                       X       X     X     X
News and Newsletters...........  Asia Pulse                           X       X     X     X
                                 Comtex News                          X       X     X     X
                                 Phillips Newsletters                 X       X     X     X
                                 Reuters News                         X       X     X     X
Business and Trade Press.......  Responsive Database Services         X       X     X     X
                                 Information Access Company           X       X     X     X
Executive Biographies..........  Marquis Who's Who                    X       X
                                 Standard & Poor's Register           X       X
Stock Quotes...................  Datastream                                         X
                                 Quote.com                            X       X
Investment Reports.............  Investext                            X       X     X
Published Statistical Tables...  Responsive Database Services         X       X
SEC Filings....................  EDGAR                                X       X
We enter into contracts with our information providers which are generally
for a term of at least one year, and which renew for the same period if not
canceled with advance notice. These contracts may be terminated under certain
circumstances. For more information, see "Risk Factors--We depend entirely on
our information providers for content." Under these arrangements, royalties are
generally paid on a quarterly basis to information providers. Royalties are
typically calculated either as a flat percentage of our revenues or as a
per-user fee that declines as the number of authorized users of the product
increases. In limited cases, we pay a fixed fee per period for unlimited use of
the information.
 
                                       38
40
 
CUSTOMERS
 
     At December 31, 1998, 445 organizations had subscribed to our Web-based
Business Browser product line, up from 233 at December 31, 1997. On average, our
customers at December 31, 1998 had an annualized contract value of $58,248 per
customer, compared to $38,512 per customer at December 31, 1997. The annualized
contract value of customer contracts for Business Browser products was $25.9
million at December 31, 1998, having grown from $9.0 million at December 31,
1997. The following is a representative list of significant customers in each of
our primary industry sectors:
 
PROFESSIONAL SERVICES
Arthur Andersen
Arthur D. Little
Bain & Company
Cambridge Technology Partners
Deloitte & Touche
EDS
Ernst & Young
KPMG
Watson Wyatt
 
OTHER CORPORATIONS
Avery Dennison
Bayer
Boeing
Cargill
Coca Cola
General Electric
Johnson & Johnson
Pitney Bowes
Sears

FINANCIAL SERVICES
American Express
BankAmerica
Bank of Tokyo
Bear Stearns
Credit Lyonnais
First Union Bank
Merrill Lynch
Oppenheimer
Royal Bank of Canada
 
BUSINESS SCHOOLS
Dartmouth
Duke
Harvard
Stanford
University of Florida
University of Southern California
University of Texas
Yale

TECHNOLOGY
AT&T
British Telecom
Compaq
GTE
JD Edwards
Lockheed Martin
MCI/Worldcom
Nortel
Oracle
PeopleSoft
SAP
Sun Microsystems
 
     At December 31, 1998, approximately 60% of our annualized contract value
for Web-based products came from customers in the professional services and
financial services sectors, which have been the traditional customers for
business information products. The remaining 40% of our annualized contract
value at December 31, 1998 for Web-based products represented customers in
sectors that have not historically been heavy consumers of business information
products. At these customers, Business Browser products are used by
professionals throughout the organization, including sales, marketing, finance
and management personnel, as a result of the products' ease of use and
availability over the Web.
 
SALES AND MARKETING
 
     We market our products through a direct sales force and marketing staff,
which as of December 31, 1998 consisted of 67 full-time employees based at five
locations throughout the US and one location in the UK. The sales function
breaks down into two major parts:
 
        - the initial sale, which is conducted by account executives
 
        - customer retention and growth through the sale of additional seats and
          upgrades, which are primarily handled by account managers
 
                                       39
41
 
     As of December 31, 1998, we had 20 account executives and 12 account
managers. Compensation for account executives and account managers is comprised
of base salary plus commission. The commission component typically constitutes
50% and 40% of the compensation of account executives and account managers,
respectively. We also employ a telemarketing group which assists in generating
leads for the account executives. As of December 31, 1998, there were ten
members of the telemarketing group.
 
     Business Browser products are sold on a subscription basis, generally for a
one-year period. Customers typically prepay for annual subscriptions. Typically,
contracts automatically renew for the same period prior to expiration unless
canceled by the client. The Business Browser product line is available at a
fixed annual subscription price which declines on a per-user basis as the total
number of users increases. The fixed-price model encourages business
professionals to use the products as needed without concern with additional
charges, and a declining marginal price per user encourages customers to
distribute the products widely throughout their organizations. List prices as of
January 1, 1999 ranged from $20,000 per year for a single user seat to $290,000
per year for 1,000 user seats.
 
CUSTOMER SUPPORT
 
     We provide both on-site and telephone support for clients. As of December
31, 1998, we had eight field support consultants who provide assistance before
and after sales are completed. For example, they assist in managing a product
trial for a prospective customer and expanding the availability of our products
to additional users through training and rollout initiatives within an
organization. They also provide technical consulting which may be requested,
such as the customization of Web pages for large clients or the building of
prototype applications using AppLink.
 
     As of December 31, 1998, we had six telephone-based customer support
representatives in the U.S. and one in the UK. These representatives operate the
telephone help desk which is open from 8:00 a.m. to 8:00 p.m. Monday through
Friday.
 
WEBSITE TECHNOLOGY AND OPERATIONS
 
     OneSource has designed its Website architecture to be open, flexible,
scaleable and reliable. The architecture is designed to accommodate an evolving
collection of third-party technologies that together provide the functionality
required by our products' applications. These technologies are adapted and
integrated with software developed in-house. As a result, we believe our systems
are flexible enough to upgrade or change software as new, improved third-party
software products are developed or as we develop our own new software.
 
     Our on-line architecture was also designed to be able to expand easily and
efficiently as usage grows. By treating the core backoffice technologies as
system "objects," we have constructed a natural environment for simply adding
additional copies of specific servers, as needed, to share the load. Besides
load sharing and usage expansion, this setup also provides natural failover
capabilities for the system. Any given server can suffer a problem and one or
several backups share the load while the problem is corrected.
 
     The OneSource on-line site is located at a dedicated hosting facility
managed by GTE/BBN Internetworking. It is a node on the GTE/BBN Internet
backbone. The system is available 24
 
                                       40
42
 
hours a day, seven days a week. For more information, see "Risk Factors--If our
Website service is disrupted, our business would be adversely affected."
 
     The engineering team closely monitors the usage, delivery performance and
availability of the system. Particular attention is paid to individual product
usage, relative levels of customer activity, speed of data retrieval and
delivery, peak usage figures, uptime statistics and power requirements. This
engineering team is key to maintaining continuous service for our customers.
 
COMPETITION
 
     The business information services industry is intensely competitive. We
face direct or indirect competition from the following types of companies:
 
        - large, well-established business and financial information providers
          such as Dow Jones, Dialog, Lexis-Nexis, Pearson, Reuters, Thomson,
          Primark and McGraw-Hill
 
        - on-line information services or Websites targeted to specific markets
          or applications, such as NewsEdge, Factset and Bloomberg
 
        - providers of sales, marketing and credit information such as Dun &
          Bradstreet
 
        - Web retrieval, other Web "portal" companies and other free or low-cost
          mass market on-line services such as Excite, Infoseek, Lycos, Yahoo!
          and AOL/Netscape
 
     Many of our existing competitors, as well as a number of prospective
competitors, have longer operating histories, greater name recognition, larger
customer bases and significantly greater financial, technical and marketing
resources than we do. Certain of our competitors offer financial and business
information free of charge with the goal of achieving high enough usage to
facilitate the sale of substantial amounts of advertising. To the extent these
types of competitors offer products free of charge that are similar to ours, it
would have a material adverse impact on our business, financial condition and
results of operations. In addition, there are relatively low barriers to entry
to the Web-based information market and we may face additional competition from
new entrants. For more information, see "Risk Factors--We face intense
competition from other companies."
 
     The principal competitive factors in our industry are availability of
comprehensive and integrated business and financial information, ease of use,
support and training required and price/performance characteristics. We believe
that Business Browser products are differentiated from the products offered by
other providers because of our ability to deliver information from many
different, competing providers on an enterprise-wide basis. We also believe that
our focus on integrating and presenting information so that interpretation,
manipulation and analysis can be performed more easily also differentiates our
products.
 
EMPLOYEES
 
     We had 166 full-time employees as of December 31, 1998, including 67 in
sales and marketing, 22 in engineering, 14 in production/on-line support, 25 in
finance and administration and 38 on our Global Strategic Web Applications Team.
Our employees are not represented by any collective bargaining organization. We
have never experienced a work stoppage and we believe our relationships with our
employees are good.
 
                                       41
43
 
FACILITIES
 
     Our corporate headquarters are located in a 28,766 square foot rented
facility in Cambridge, Massachusetts, under a lease expiring in July 1999. We
have entered into a new lease for a new, 35,766 square foot headquarters
facility in Concord, Massachusetts. We intend to move to that facility in June
1999. Our lease to the new facility expires in May 2004. We lease additional
sales offices in Chicago, New York, Los Angeles, San Francisco and London,
England. We believe that these facilities and additional or alternative space
available to us will be adequate to meet our needs for the foreseeable future.
 
LITIGATION
 
     OneSource is not a party to any material legal proceedings.
 
                                       42
44
 
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
 
     The following table sets forth certain information with respect to the
executive officers and directors of OneSource as of March 1, 1999.
AGE                          POSITION
NAME                          ---                          --------
Martin Kahn(1)(2)...........  48    Chairman of the Board of Directors
Daniel J. Schimmel..........  39    President, Chief Executive Officer and Director
James A. Becker.............  41    Vice President, Global Strategic Web Applications Team
Philip J. Garlick...........  37    Vice President, Global Enterprise Sales and Marketing
Mark C. VanDine.............  42    Vice President, Engineering
Roy D. Landon...............  43    Vice President, Finance and Administration
David Dominik(1)............  42    Director
Gregg S. Newmark(2).........  40    Director
------------
(1) Member of Compensation Committee.
 
(2) Member of Audit Committee.
 
     Martin Kahn joined OneSource as Chairman of the Board of Directors in
September 1993. Mr. Kahn has served as managing director of Cadence Information
Associates LLC since 1996. Mr. Kahn was the chairman of Ovid Technologies, Inc.,
a producer of medical, scientific and technical CD Rom and network products,
from 1990 to 1998, was chairman of VISTA Information Solutions, Inc., a supplier
of information about geographically-based risk, from 1992 to 1996 and was
chairman of Shoppers Express, Inc., an Internet-based grocery shopping service,
from 1995 to 1998. Mr. Kahn holds an MBA from the Harvard Business School and a
B.A. from Yale University.
 
     Daniel J. Schimmel joined OneSource as President, Chief Executive Officer
and a Director in 1993. Prior to joining OneSource, Mr. Schimmel served as
general manager of the OneSource Division and held other operating positions at
Lotus. Mr. Schimmel holds an MBA from the Harvard Business School and a B.A.
from Harvard University.
 
     James A. Becker joined OneSource as the Director of Product Management in
1993 and became Vice President, Global Strategic Web Applications Team in 1995.
Prior to joining OneSource, Mr. Becker served as group product manager at Lotus.
Mr. Becker holds an MBA from the Yale School of Management and a B.A. from Brown
University.
 
     Philip J. Garlick joined OneSource as Director of Marketing and Product
Development in 1993, served as Vice President and General Manager Europe from
1995 to October 1997, and in October 1997 became Vice President, Global
Enterprise Sales and Marketing. Prior to joining OneSource, Mr. Garlick was a
marketing executive at Lotus UK. Mr. Garlick holds an MA in Economics and a B.A.
from Manchester University.
 
     Mark C. VanDine joined OneSource as Senior Product Manager in 1993, served
as Director, Platform Product Management in 1995 and in 1996 became Vice
President, Engineering. Prior to joining OneSource, Mr. VanDine was a senior
consultant at Lotus. Mr. VanDine holds a B.A. and an MBA from Penn State
University.
 
                                       43
45
 
     Roy D. Landon joined OneSource as Director, Finance and Administration in
1993 and became Vice President, Finance and Administration in 1997. Prior to
joining OneSource, Mr. Landon was director of plans and controls for the
Consulting and Information Services Group at Lotus. Mr. Landon holds a B.S. from
Babson College.
 
     David Dominik joined OneSource as a Director in 1993. Mr. Dominik has been
a managing director at Bain Capital Inc. since January 1990. He is also a
director of Oacis Healthcare Holdings Corp., a clinical information systems
software company.
 
     Gregg S. Newmark joined OneSource as a Director in 1993. Since 1993 Mr.
Newmark has served as general partner of William Blair Venture Partners, as a
principal of William Blair & Company, L.L.C. and as a managing director of
William Blair Capital Partners.
 
ELECTION OF OFFICERS AND DIRECTORS
 
     The executive officers of OneSource are elected by the Board of Directors
on an annual basis and serve until their successors are duly elected and
qualified. Messrs. Dominik and Newmark were selected as directors of OneSource
pursuant to a Stockholders Agreement dated September 8, 1993 between OneSource
and certain of its stockholders, which agreement will terminate as of the
effective date of this offering. For more information, see "Certain
Transactions." There are no family relationships among any of the executive
officers or directors of OneSource.
 
COMMITTEES OF THE BOARD OF DIRECTORS
 
     The Board of Directors has appointed a Compensation Committee consisting of
Messrs. Kahn and Dominik. The Compensation Committee reviews and evaluates the
compensation and benefits of all officers of OneSource, reviews general policy
matters relating to compensation and benefits of OneSource employees and make
recommendations concerning these matters to the Board of Directors. The
Compensation Committee also administers OneSource's stock option and stock
purchase plans. For more information, see "--Equity Plans."
 
     The Board of Directors has also appointed an Audit Committee consisting of
Messrs. Kahn and Newmark. The Audit Committee reviews, with OneSource's
independent auditors, the scope and timing of their audit services and any other
services they are asked to perform, the auditors' report on OneSource's
consolidated financial statements following completion of their audit, and
OneSource's policies and procedures with respect to internal accounting and
financial controls. In addition, the Audit Committee will make annual
recommendations to the Board of Directors for the appointment of independent
auditors for the ensuing year.
 
DIRECTOR COMPENSATION
 
     Directors who are not employees of OneSource and who are not affiliated
with principal stockholders (also referred to as "outside directors"), will
receive an annual retainer fee and a fee for attending regular (or special)
meetings of the Board of Directors and for meetings of any committees of the
Board of Directors on which they serve, if such meetings are held separately.
Currently, Mr. Kahn is the only outside director. Outside directors also are
eligible to participate in OneSource's 1999 Stock Option and Incentive Plan.
Directors also are reimbursed for reasonable out-of-pocket expenses incurred in
attending such meetings. For more information, see "--Equity Plans," and
"Certain Transactions."
 
                                       44
46
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
     The Compensation Committee is comprised of Messrs. Kahn and Dominik.
Neither member of the Compensation Committee serves as a member of the board of
directors or compensation committee of any entity that has one or more executive
officers serving as a member of OneSource's Board of Directors or Compensation
Committee.
 
EXECUTIVE COMPENSATION
 
  Summary Compensation
 
     The following table sets forth the compensation earned by (a) the Chief
Executive Officer and (b) OneSource's four other most highly compensated
executive officers (together with the Chief Executive Officer, the "Named
Executive Officers") for services rendered in all capacities to OneSource during
the year ended December 31, 1998.
 
                           SUMMARY COMPENSATION TABLE
ANNUAL COMPENSATION(1)
                                                  -----------------------       ALL OTHER
          NAME AND PRINCIPAL POSITION               SALARY        BONUS      COMPENSATION(2)
          ---------------------------             ----------    ---------    ---------------
Daniel J. Schimmel..............................   $164,997      $57,749              --
  President and Chief Executive Officer
James A. Becker.................................    123,748       24,750              --
  Vice President, Global Strategic Web
  Applications Team
Philip J. Garlick...............................    144,000       47,520        $145,725
  Vice President, Global Enterprise Sales and
  Marketing
Mark C. VanDine.................................    115,498       23,100              --
  Vice President, Engineering
Roy D. Landon...................................    105,186       21,037              --
  Vice President, Finance and Administration
------------
(1) OneSource did not make any restricted stock awards, grant any stock
    appreciation rights or make any long-term incentive payments during 1998 to
    its executive officers. Options granted to the Named Executive Officers were
    granted at fair market value as determined by the Board of Directors based
    on all factors available to them on the grant date.
 
(2) Mr. Garlick received additional compensation in connection with his
    relocation from the UK to Massachusetts, including car and housing
    allowances, moving expenses and payment of certain taxes.
 
  Option Grants in Last Fiscal Year
 
     None of the Named Executive Officers were granted options in the year ended
December 31, 1998.
 
                                       45
47
 
  Option Exercises and Year-End Holdings
 
     The following table sets forth information concerning stock option
exercises during 1998 by each of the Named Executive Officers and the number and
value of unexercised options held by them as of December 31, 1998.
 
      AGGREGATE OPTION EXERCISES IN 1998 AND FISCAL YEAR-END OPTION VALUES
NUMBER OF SECURITIES          VALUE OF UNEXERCISED
                                                                 UNDERLYING UNEXERCISED         IN-THE-MONEY OPTIONS
                                     SHARES                    OPTIONS AT FISCAL YEAR-END       AT FISCAL YEAR-END(1)
                                   ACQUIRED ON      VALUE      ---------------------------   ---------------------------
              NAME                  EXERCISE     REALIZED(1)   EXERCISABLE   UNEXERCISABLE   EXERCISABLE   UNEXERCISABLE
              ----                 -----------   -----------   -----------   -------------   -----------   -------------
Daniel J. Schimmel...............         0              --      506,732              0                         $0
  President and Chief Executive
  Officer
James A. Becker..................    22,000                      122,000        100,000
  Vice President, Global
    Strategic
  Web Applications Team
Philip J. Garlick................         0              --       67,600        110,000
  Vice President, Global
    Enterprise
  Sales and Marketing
Mark C. VanDine..................         0              --       78,000         60,000
  Vice President, Engineering
Roy D. Landon....................         0              --       52,000         20,000
  Vice President, Finance and
  Administration
------------
(1) There was no public trading market for the common stock as of December 31,
    1998. Accordingly, these values have been calculated by determining the
    difference between the assumed initial public offering price of $        per
    share and the exercise price of the Named Executive Officer's options.
 
EQUITY PLANS
 
     1999 Stock Option and Incentive Plan.  OneSource's 1999 Stock Option and
Incentive Plan (the "1999 Stock Option Plan") was adopted by the Board of
Directors in February 1999 and approved by OneSource's stockholders in
             , 1999, to be effective upon the completion of this offering. The
1999 Stock Option Plan provides for the grant of stock-based awards to
employees, officers and directors of, and consultants or advisors to, OneSource.
Under the 1999 Stock Option Plan, OneSource may grant options that are intended
to qualify as incentive stock options ("incentive stock options") within the
meaning of Section 422 of the Internal Revenue Code of 1986, as amended (the
"Code"), options not intended to qualify as incentive stock options
("non-qualified stock options"), restricted stock and other stock-based awards.
Incentive stock options may be granted only to employees of OneSource. A total
of 800,000 shares of common stock may be issued upon the exercise of options or
other awards granted under the 1999 Stock Option Plan after the completion of
this offering. The maximum number of shares with respect to which awards may be
granted to any employee under the 1999 Stock Option Plan shall not exceed
100,000 shares of common stock during any calendar year.
 
     The 1999 Stock Option Plan is administered by the Board of Directors and
the Compensation Committee. Subject to the provisions of the 1999 Stock Option
Plan, each of the Board of Directors and the Compensation Committee has the
authority to select the persons to
 
                                       46
48
 
whom awards are granted and determine the terms of each award, including the
number of shares of common stock subject to the award. Payment of the exercise
price of an award may be made in cash, shares of common stock, a combination of
cash and stock, a promissory note or by any other method approved by the Board
or Compensation Committee, consistent with Section 422 of the Code and Rule
16b-3 under the Exchange Act. Unless otherwise permitted by the Board of
Directors, awards are not assignable or transferable except by will or the laws
of descent and distribution, and, during the participant's lifetime, may be
exercised only by the participant.
 
     The Board of Directors or Compensation Committee may, in its sole
discretion, amend, modify or terminate any award granted or made under the 1999
Stock Option Plan, so long as such amendment, modification or termination would
not materially and adversely affect the participant. The Board of Directors or
Compensation Committee may also, in its sole discretion, accelerate or extend
the date or dates on which all or any particular option or options granted under
the 1999 Stock Option Plan may be exercised.
 
     1993 Stock Purchase and Option Plan.  OneSource's 1993 Stock Purchase and
Option Plan (the "1993 Plan") was adopted by the Board of Directors and approved
by OneSource's stockholders in September 1993. Under the 1993 Plan, OneSource is
authorized to grant incentive stock options and non-qualified stock options to
employees, consultants, directors and advisors of OneSource. The aggregate
number of shares of common stock which may be issued under the 1993 Plan is
2,100,000 shares and the aggregate number of shares of Class P common stock that
may be issued under the 1993 Plan is 20,000 shares. In February 1999, the Board
of Directors, voted to terminate the 1993 Plan effective immediately prior to
the closing of this offering.
 
     To date, OneSource has granted stock options to purchase an aggregate of
1,940,548 shares of common stock pursuant to the 1993 Plan.
 
     1999 Employee Stock Purchase Plan.  The 1999 Employee Stock Purchase Plan
(the "1999 Purchase Plan") was adopted by the Board of Directors in February
1999 and approved by OneSource's stockholders in                 1999, to be
effective upon the completion of this offering. The 1999 Purchase Plan provides
for the issuance of a maximum of 100,000 shares of common stock after the
completion of this offering.
 
     The 1999 Purchase Plan is administered by the Compensation Committee of the
Board of Directors. All employees of OneSource whose customary employment is for
more than 20 hours per week and for more than three months in any calendar year
and who have completed more than 180 days of employment with OneSource on or
before the first day of any Payment Period (as defined below) are eligible to
participate in the 1999 Purchase Plan. Employees who would own 5% or more of the
total combined voting power or value of OneSource's stock immediately after the
grant may not participate in the 1999 Purchase Plan. To participate in the 1999
Purchase Plan, an employee must authorize OneSource to deduct an amount (not
less than one percent nor more than 10 percent of a participant's total cash
compensation) from his or her pay during six-month payment periods (each, a
"Payment Period"). The first Payment Period will commence upon the registration
of OneSource's common stock under the Exchange Act and will end on the earlier
of the following                 or                 . Thereafter, the Payment
Periods will commence on the six-month periods commencing on                 1
and                 1, respectively, and ending on the following
                and                 ,
 
                                       47
49
 
respectively, of each year, but in no case shall an employee be entitled to
purchase more than                 shares in any one Payment Period. The
exercise price for the option granted in each Payment Period is 85% of the
lesser of the average market price of the common stock on the first or last
business day of the Payment Period, in either event rounded up to the nearest
cent to avoid fractions of a dollar other than  1/4, 1/2 and  3/4. If an
employee is not a participant on the last day of the Payment Period, such
employee is not entitled to exercise his or her option, and the amount of his or
her accumulated payroll deductions will be refunded. Options granted under the
1999 Purchase Plan may not be transferred or assigned. An employee's rights
under the 1999 Purchase Plan terminate upon his or her voluntary withdrawal from
the plan at any time or upon termination of employment. No options have been
granted to date under the 1999 Purchase Plan.
 
401(K) PLAN
 
     OneSource has established a tax-qualified employee savings and retirement
plan. Employees must complete three months of service at OneSource before they
are eligible to participate on the first day of the month following the
completion. Employees may contribute a percentage of their pre-tax compensation
and OneSource may, in its discretion from year-to-year, make matching
contributions to the employees. Amounts matched by OneSource vest over three
years.
 
LIMITATION OF LIABILITY AND INDEMNIFICATION OF OFFICERS AND DIRECTORS
 
     OneSource's Restated Certificate of Incorporation and Amended and Restated
By-Laws provide that the directors and officers of OneSource shall be
indemnified by OneSource to the fullest extent authorized by Delaware law, as it
now exists or may in the future be amended, against all expenses and liabilities
reasonably incurred in connection with their service for or on behalf of
OneSource. In addition, the Restated Certificate of Incorporation provides that
the directors of OneSource will not be personally liable for monetary damages to
OneSource for breaches of their fiduciary duty as directors, unless they
violated their duty of loyalty to OneSource or its stockholders, acted in bad
faith, knowingly or intentionally violated the law, authorized illegal dividends
or redemptions or derived an improper personal benefit from their action as
directors. OneSource intends to obtain insurance which insures the directors and
officers of OneSource against certain losses and which insures OneSource against
certain of its obligations to indemnify such directors and officers.
 
                                       48
50
 
                              CERTAIN TRANSACTIONS
 
     In connection with the management buy-out from Lotus in 1993, each of
William Blair Venture Partners III Limited Partnership and Information Partners
Capital Fund, L.P. and its affiliated entities purchased 162,000 shares of Class
P common stock for $1.62 million, or $10.00 per share, and 1,458,000 shares of
common stock for $180,000, or $0.12 per share. The shares of common stock held
by William Blair Venture Partners and Information Partners Capital are subject
to registration rights entitling the holder to demand that OneSource register
the shares under the Securities Act in certain circumstances to enable the
holder to resell its shares. For more information, see "Shares Eligible For
Future Sale." A Stockholders Agreement among OneSource, William Blair Venture
Partners, Information Partners Capital and certain other stockholders provides
that, for so long as William Blair Venture Partners or Information Partners
Capital continues to own at least 25% of the common stock which each such entity
originally purchased in the buy-out, OneSource shall cause a representative of
each of William Blair Venture Partners and Information Partners Capital to be
nominated to the Board of Directors. Mr. Newmark, a general partner of William
Blair Venture Management Company (the general partner of William Blair Venture
Partners), currently serves as the William Blair Venture Partners representative
and Mr. Dominik, a general partner of Information Partners, Inc. (the general
partner of Information Partners Capital), currently serves as the Information
Partners Capital representative. The Stockholders Agreement will be terminated
upon consummation of this offering.
 
     Since 1993, OneSource has paid each of William Blair Venture Partners and
an affiliate of Information Partners Capital an annual management fee of $0.1
million, pursuant to an oral arrangement. OneSource has agreed to pay each of
these entities a one-time fee of $0.5 million to terminate the management fee
arrangement.
 
     OneSource intends to use approximately $6.7 million of its net proceeds
from this offering to repay a note issued by OneSource to Lotus in connection
with the purchase of OneSource's business from Lotus in 1993. The note bears
interest at the rate of 8% per year and is due September 8, 2000, unless
accelerated upon certain events. The completion of this offering would require
OneSource to repay a significant portion of the note if it is not repaid in
full.
 
                                       49
51
 
                       PRINCIPAL AND SELLING STOCKHOLDERS
 
     The following table sets forth certain information known to OneSource
regarding beneficial ownership of OneSource's common stock as of March 1, 1999
and as adjusted to reflect the sale of the shares of common stock in this
offering by (a) each person known by OneSource to be the beneficial owner of
more than 5% of OneSource's common stock; (b) each of OneSource's directors; (c)
each Named Executive Officer (for more information, see "Management--Executive
Compensation"); (d) all executive officers and directors as a group; and (e)
each selling stockholder. Unless otherwise indicated, to the knowledge of
OneSource, each stockholder possesses sole voting and investment power with
respect to the shares listed, except to the extent an individual stockholder's
shares are owned jointly with that person's spouse.
SHARES BENEFICIALLY                 SHARES BENEFICIALLY
                                            OWNED PRIOR TO THE                    OWNED AFTER THE
                                                OFFERING(1)                       OFFERING(1)(2)
                                            -------------------                 -------------------
                                            NUMBER OF               SHARES      NUMBER OF
 NAME AND ADDRESS OF BENEFICIAL OWNER(3)     SHARES     PERCENT   OFFERED(2)     SHARES     PERCENT
 ---------------------------------------    ---------   -------   -----------   ---------   -------
Information Partners Capital Fund,
  L.P.(4).................................  1,619,999    44.0%
William Blair Venture Partners III Limited
  Partnership(5)..........................  1,620,000    44.0
Martin Kahn(6)............................    329,364     8.4
Daniel J. Schimmel(7).....................    586,732    14.0
James A. Becker(8)........................    166,000     4.5
Philip J. Garlick(9)......................     71,600     1.9
Mark C. Van Dine(10)......................     86,000     2.3
Roy D. Landon(11).........................     60,000     1.6
David Dominik(4)..........................  1,619,999    44.0
Gregg Newmark(5)..........................  1,620,000    44.0
Lotus Development Corporation(12).........    200,000     5.2
All executive officers and directors as a
  group (8 persons)(13)...................  4,539,695    95.4
------------
 (1) Based on         shares of common stock outstanding prior to the offering
     and         outstanding upon completion of the offering. The number of
     shares of common stock deemed outstanding includes (a) one share of common
     stock for each share of outstanding Class P common stock and (b) shares
     issuable pursuant to options held by the respective person or group which
     may be exercised within 60 days after March 1, 1999 ("presently exercisable
     stock options"), as set forth in the other footnotes to this table,
     including options to purchase             shares that are being exercised
     by certain of the selling stockholders in connection with this offering.
     For purposes of calculating each person's or group's percentage ownership,
     presently exercisable stock options are included for that person or group
     but not the presently exercisable stock options of any other person or
     group.
 
 (2) Assumes that the Underwriters' over-allotment option to purchase up to an
     additional             shares from the selling stockholders is not
     exercised. If the Underwriters exercise their over-allotment option to
     purchase up to an additional             shares, then the following
     stockholders will sell up to the following number of additional shares:
 
 (3) For more information, see "Management--Executive Officers and Directors."
     Unless otherwise indicated, the address for each beneficial owner is c/o
     OneSource Information Services, Inc., 150 CambridgePark Drive, Cambridge,
     MA 02140.
 
 (4) Includes 55,933 shares owned by BCIP Associates and 60,613 shares owned by
     BCIP Trust Associates, L.P. The respective general partners of these
     entities, including Mr. Dominik, exercise sole voting and investment power
     with respect to the shares owned by such entities. Each of these persons
     disclaims beneficial ownership of such shares except to the extent of his
     respective proportionate pecuniary interest therein.
 
                                       50
52
 
 (5) The general partners of this entity, including Mr. Newmark, exercise sole
     voting and investment power with respect to the shares owned by such
     entity. Each of these persons disclaims beneficial ownership of such shares
     except to the extent of his respective proportionate pecuniary interest
     therein.
 
 (6) Includes 249,364 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
 (7) Includes 506,732 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
 (8) Includes 122,000 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
 (9) Includes 67,600 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
(10) Includes 78,000 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
(11) Includes 52,000 shares of common stock issuable pursuant to stock options
     that are exercisable within 60 days of March 1, 1999.
 
(12) Lotus Development Corporation's address is 55 Cambridge Parkway, Cambridge,
     MA 02142. All of such shares are issuable pursuant to a currently
     exercisable warrant.
 
(13) Please reference notes 5 through 11 inclusive. Includes 1,075,696 shares of
     common stock issuable pursuant to stock options that are exercisable within
     60 days of March 1, 1999.
 
                          DESCRIPTION OF CAPITAL STOCK
 
     Effective upon the closing of this offering and the filing of OneSource's
Restated Certificate of Incorporation, the authorized capital stock of OneSource
will consist of 20,000,000 shares of common stock, par value $.01 per share, and
1,000,000 shares of preferred stock, par value $.01 per share.
 
     Prior to the closing of this offering and in accordance with OneSource's
Certificate of Incorporation as currently in effect, OneSource is authorized to
issue up to 6,500,000 shares of common stock, par value $.01 per share, of which
3,329,392 shares are issued and outstanding and 500,000 shares of Class P common
stock, par value $.01 per share, of which 352,400 shares are issued and
outstanding. Prior to the closing of this offering, all shares of Class P common
stock and preference amount thereon will be reclassified into            shares
of common stock.
 
     The following summary description of OneSource's capital stock is not
intended to be complete and is qualified by reference to the provisions of
applicable law and to OneSource's Restated Certificate of Incorporation and
Amended and Restated By-laws filed as exhibits to the registration statement of
which this prospectus is a part.
 
COMMON STOCK
 
     As of March 1, 1999, there were 3,329,392 shares of common stock
outstanding held by 42 stockholders of record. Based upon the number of shares
outstanding as of that date and giving effect to the issuance of the
                shares of common stock offered by OneSource in this offering and
the reclassification of each outstanding share of Class P common stock into one
share of common stock plus an additional number of shares of common stock
determined by dividing the preference amount for such shares by the assumed
initial public offering price of $        per share and the repurchase of
such           additional shares of common stock by OneSource, there will be
                shares of common stock outstanding upon the closing of this
offering. In addition, as of              , 1999, there were outstanding stock
options for the purchase of a total of                 shares of common stock
and outstanding warrants for the purchase of         shares of common stock.
 
                                       51
53
 
     Holders of common stock are entitled to one vote for each share held on all
matters submitted to a vote of stockholders and do not have cumulative voting
rights. Directors are elected by a plurality of the votes of the shares present
in person or by proxy at the meeting and entitled to vote in such election.
Holders of common stock are entitled to receive ratably such dividends, if any,
as may be declared by the Board of Directors out of funds legally available
therefor, subject to any preferential dividend rights of outstanding preferred
stock. Upon the liquidation, dissolution or winding up of OneSource, the holders
of common stock are entitled to receive ratably the net assets of OneSource
available after the payment of all debts and other liabilities of OneSource,
subject to the prior rights of any outstanding preferred stock. Holders of the
common stock have no preemptive, subscription, redemption or conversion rights,
nor are they entitled to the benefit of any sinking fund. The outstanding shares
of common stock are, and the shares offered by OneSource in this offering will
be, when issued and paid for, validly issued, fully paid and nonassessable. The
rights, powers, preferences and privileges of holders of common stock are
subject to, and may be adversely affected by, the rights of the holders of
shares of any series of preferred stock which OneSource may designate and issue
in the future.
 
PREFERRED STOCK
 
     The Board of Directors will be authorized, subject to any limitations
prescribed by law, without further stockholder approval, to issue from time to
time up to an aggregate of 1,000,000 shares of preferred stock, in one or more
series. Each such series of preferred stock shall have such number of shares,
designations, preferences, voting powers, qualifications and special or relative
rights or privileges as shall be determined by the Board of Directors, which may
include, among others, dividend rights, voting rights, redemption and sinking
fund provisions, liquidation preferences, conversion rights and preemptive
rights.
 
     The stockholders of OneSource have granted the Board of Directors authority
to issue the preferred stock and to determine its rights and preferences in
order to eliminate delays associated with a stockholder vote on specific
issuances. The rights of the holders of common stock will be subject to the
rights of holders of any preferred stock issued in the future. The issuance of
preferred stock, while providing desirable flexibility in connection with
possible acquisitions and other corporate purposes, could adversely affect the
voting power or other rights of the holders of common stock, and could make it
more difficult for a third-party to acquire, or discourage a third-party from
attempting to acquire, a majority of the outstanding voting stock of OneSource.
OneSource has not, to date, issued any shares of preferred stock and has no
present plans to issue any shares of preferred stock.
 
DELAWARE LAW AND CERTAIN CHARTER AND BY-LAW PROVISIONS; ANTI-TAKEOVER EFFECTS
 
     Upon completion of this offering, OneSource will be subject to the
provisions of Section 203 of the General Corporation Law of Delaware. Section
203 prohibits a publicly-held Delaware corporation from engaging in a "business
combination" with an "interested stockholder" for a period of three years after
the date of the transaction in which the person became an interested
stockholder, unless the business combination is approved in a prescribed manner.
A "business combination" includes mergers, asset sales and other transactions
resulting in a financial benefit to the interested stockholder. Subject to
certain exceptions, an "interested stockholder" is a person who, together with
affiliates and associates, owns, or within the prior three years did own, 15% or
more of the corporation's outstanding voting stock.
 
                                       52
54
 
     The Restated Certificate of Incorporation provides that directors may be
removed only for cause by the affirmative vote of the holders of 75% of the
shares of capital stock of OneSource entitled to vote. In addition, under the
Restated Certificate of Incorporation any vacancy on the Board of Directors,
however occurring, including a vacancy resulting from an enlargement of the
Board, may only be filled by vote of a majority of the directors then in office.
The likely effect of the limitations on the removal of directors and filling of
vacancies is an increase in the time required for the stockholders to change the
composition of the Board of Directors.
 
     The Restated By-Laws to be adopted upon the closing of this offering
provide that any action required or permitted to be taken by the stockholders of
OneSource at an annual meeting or special meeting of stockholders may only be
taken if OneSource is given proper advance notice of the action. The Restated
By-Laws further provide that special meetings of stockholders may only be called
by a majority of the Board of Directors, the Chairman of the Board of Directors
or the President of OneSource. The foregoing provisions could have the effect of
delaying until the next stockholders meeting stockholder actions which are
favored by the holders of a majority of the outstanding voting securities of
OneSource. However, the Restated By-Laws provide that stockholders may take
action by written consent.
 
     The General Corporation Law of Delaware provides generally that the
affirmative vote of a majority of the shares entitled to vote on any matter is
required to amend a corporation's certificate of incorporation or by-laws,
unless a corporation's certificate of incorporation or by-laws, as the case may
be, requires a greater percentage. The Restated By-Laws require the affirmative
vote of the holders of at least 75% of the issued and outstanding shares of
capital stock of OneSource entitled to vote to amend or repeal any of the
foregoing provisions of the Restated By-Laws. The 75% stockholder vote would be
in addition to any separate class vote that might be required pursuant to the
terms of any series of preferred stock that might be outstanding at the time any
such amendments are submitted to stockholders.
 
TRANSFER AGENT AND REGISTRAR
 
     The transfer agent and registrar for the common stock will be
                .
 
                                       53
55
 
                        SHARES ELIGIBLE FOR FUTURE SALE
 
     Upon completion of this offering, OneSource will have
shares of common stock outstanding (assuming no exercise of the outstanding
options or warrants). Of these shares, the                 shares
(                shares if the over-allotment option is exercised in full) to be
sold in this offering will be freely tradable without restriction or further
registration under the Securities Act, except that any shares purchased by
affiliates of OneSource, as that term is defined in Rule 144 under the
Securities Act ("Affiliates"), may generally only be sold in compliance with the
limitations of Rule 144 described below.
 
SALES OF RESTRICTED SHARES
 
     The remaining                 shares of common stock outstanding upon
completion of this offering are deemed "Restricted Shares" under Rule 144 or
Rule 701 under the Securities Act. Approximately                 of such
Restricted Shares will be eligible for sale in the public market pursuant to
Rule 144(k) on the date of this prospectus. Upon expiration of certain lock-up
agreements, 180 days after the date of this prospectus, an additional
                shares of common stock will be eligible for sale in the public
market pursuant to Rule 144 under the Securities Act.
 
     In general, under Rule 144, a person (or persons whose shares are
aggregated), including an Affiliate, who has beneficially owned Restricted
Shares for at least one year is entitled to sell, within any three-month period,
a number of such shares that does not exceed the greater of (a) one percent of
the then outstanding shares of common stock (approximately         shares
immediately after this offering) or (b) the average weekly trading volume in the
common stock in the over-the-counter market during the four calendar weeks
preceding the date on which notice of such sale is filed, provided certain
requirements concerning availability of public information, manner of sale and
notice of sale are satisfied. In addition, Affiliates must comply with the
restrictions and requirements of Rule 144, other than the one-year holding
period requirement, in order to sell shares of common stock which are not
Restricted Shares. Under Rule 144(k), a person who is not an Affiliate and has
not been an Affiliate for at least three months prior to the sale and who has
beneficially owned Restricted Shares for at least two years may resell such
shares without compliance with the foregoing requirements. In meeting the one-
and two-year holding periods described above, a holder of Restricted Shares can
include the holding periods of a prior owner who was not an Affiliate. The one-
and two-year holding periods described above do not begin to run until the full
purchase price or other consideration is paid by the person acquiring the
Restricted Shares from the issuer or an Affiliate. Rule 701 provides that
currently outstanding shares of common stock acquired under OneSource's employee
compensation plans may be resold by persons, other than Affiliates, beginning 90
days after the date of this prospectus, subject only to the manner of sale
provisions of Rule 144, and by Affiliates under Rule 144, without compliance
with its one-year minimum holding period, subject to certain limitations.
 
OPTIONS
 
     Rule 701 also provides that the shares of common stock acquired upon the
exercise of currently outstanding options or pursuant to other rights granted
under OneSource's stock plans may be resold by persons, other than Affiliates,
beginning 90 days after the date of this prospectus, subject only to the manner
of sale provisions of Rule 144, and by Affiliates under
 
                                       54
56
 
Rule 144, without compliance with its one-year minimum holding period, subject
to certain limitations. As of the date of this prospectus, the Board of
Directors has authorized an aggregate of up to                 shares of common
stock for issuance pursuant to OneSource's stock option and stock purchase
plans. At the date of this prospectus,                 shares of common stock
are issuable pursuant to outstanding vested options or pursuant to other rights
granted under OneSource's stock plan(s), of which approximately
                shares are not subject to lock-up agreements with the
Underwriters and will be eligible for sale in the public market in accordance
with Rule 701 under the Securities Act beginning 90 days after the date of this
prospectus;                 shares of common stock are issuable pursuant to
outstanding options that are not yet exercisable; and                 shares of
common stock are available for future grants under OneSource's stock option and
stock purchase plans.
 
     OneSource intends to file one or more registration statements on Form S-8
under the Securities Act 180 days after the date of this prospectus to register
all shares of common stock which are issuable pursuant to OneSource's stock
option and stock purchase plans. Such registration statements are expected to
become effective upon filing. Shares covered by such registration statements
will thereupon be eligible for sale in the public markets.
 
LOCK-UP AGREEMENTS
 
     With certain exceptions, OneSource, its executive officers and directors,
the selling stockholders and certain other security-holders have agreed not to
sell or transfer any shares of common stock (or any security convertible into or
exchangeable or exercisable for common stock), or to engage in certain hedging
transactions with respect to the common stock without the prior written consent
of William Blair & Company, L.L.C. ("William Blair") for a period of 180 days
from the date of this prospectus. In addition, for a period of 180 days from the
date of this prospectus, except as required by law, OneSource has agreed that
its Board of Directors will not consent to any offer for sale, sale or other
disposition, or any transaction which is designed or could be expected to result
in the disposition by any person, directly or indirectly, of any shares of
common stock without the prior written consent of William Blair. For more
information, see "Underwriting." William Blair in its sole discretion at any
time or from time to time and without notice may release for sale in the public
market all or any portion of the shares subject to the lock-up agreements.
 
REGISTRATION RIGHTS
 
     Upon the expiration of the contractual lock-up period, certain security
holders of OneSource (the "Rights Holders") will be entitled to require
OneSource to register under the Securities Act up to a total of
                shares of outstanding common stock (the "Registrable Shares")
under the terms of an agreement between OneSource and the Rights Holders (the
"Registration Rights Agreement"). The Registration Rights Agreement provides
that if OneSource proposes to register in a firm commitment underwritten
offering any of its securities under the Securities Act at any time or times,
the Rights Holders, subject to certain exceptions, shall be entitled to include
Registrable Shares in such registration. However, the managing underwriter of
any such offering may exclude for marketing reasons some or all of such
Registrable Shares from such registration. The Rights Holders also have, subject
to certain conditions and limitations, the right to require OneSource, no more
than once in any six-month period, to prepare and file a registration statement
under the Securities Act with respect to their
 
                                       55
57
 
Registrable Shares. OneSource is generally required to bear the expenses of all
such registrations, except underwriting discounts and commissions.
 
     Prior to this offering, there has been no public market for the common
stock of OneSource, and no predictions can be made as to the effect, if any,
that market sales of shares of common stock prevailing from time to time, or the
availability of shares for future sale, may have on the market price for our
common stock. Sales of substantial amounts of common stock, or the perception
that such sales could occur, could adversely affect prevailing market prices for
our common stock and could impair OneSource's future ability to obtain capital
through an offering of equity securities.
 
                                       56
58
 
                                  UNDERWRITING
 
     Each Underwriter named below has agreed to purchase from OneSource and the
selling stockholders the number of shares of common stock set forth opposite its
name.
NUMBER OF
                        UNDERWRITER                            SHARES
                        -----------                           ---------
William Blair & Company, L.L.C. ............................
U.S. Bancorp Piper Jaffray Inc. ............................
Adams, Harkness & Hill, Inc. ...............................
                                                              --------
     Total..................................................
This offering will be underwritten on a firm commitment basis. In the
Underwriting Agreement among OneSource, the selling stockholders and the
Underwriters, the Underwriters have agreed, subject to the terms and conditions
set forth therein, to purchase the shares of common stock being sold pursuant
thereto at a price per share equal to the public offering price less the
underwriting discount specified on the cover page of this prospectus. According
to the terms of the Underwriting Agreement, the Underwriters will either
purchase all of the shares or none of them. In the event of default by any
Underwriter, in certain circumstances the purchase commitments of the
non-defaulting Underwriters may be increased or the Underwriting Agreement may
be terminated. William Blair, U.S. Bancorp Piper Jaffray Inc. and Adams,
Harkness & Hill, Inc. are acting as the representatives of the Underwriters.
 
     The representatives of the Underwriters have advised OneSource and the
selling stockholders that the Underwriters will offer the shares of common stock
to the public at the public offering price specified on the cover page of this
prospectus. The Underwriters may also offer the shares to certain dealers at the
public offering price less a concession of up to $     per share. The
Underwriters may allow, and these dealers may re-allow, a concession of up to
$     per share to certain other dealers. The Underwriters will offer the shares
subject to prior sale and subject to receipt and acceptance of the shares by the
Underwriters. The Underwriters may reject any order to purchase shares in whole
or in part. The Underwriters expect that OneSource and the selling stockholders
will deliver the shares to the Underwriters through the facilities of the
Depository Trust Company in New York, New York on or about              , 1999.
At that time, the Underwriters will pay OneSource and the selling stockholders
for the shares in immediately available funds. After the commencement of the
initial public offering, the representatives may change the offering price and
the other selling terms.
 
     The Underwriters have the option to purchase up to an aggregate of
                additional shares of common stock from the selling stockholders
at the same price they are paying for the                 shares offered hereby.
The Underwriters may purchase additional shares only to cover over-allotments
made in connection with this offering and only within 30 days after the date of
this prospectus. If the Underwriters decide to exercise this over-allotment
option, each Underwriter will be required to purchase additional shares in
approximately the same proportion as set forth in the table above. The
Underwriters will offer any additional shares that they purchase on the terms
described in the preceding paragraph.
 
                                       57
59
 
     The following table summarizes the compensation to be paid by OneSource and
the selling stockholders to the Underwriters:
TOTAL
                                                     ---------------------------------------------
                                        PER SHARE    WITHOUT OVER-ALLOTMENT    WITH OVER-ALLOTMENT
                                        ---------    ----------------------    -------------------
Public Offering Price.................
Underwriting Discount paid by
  OneSource...........................
Underwriting Discount paid by the
  selling stockholders................
OneSource estimates the expenses of this offering payable by OneSource
(excluding the underwriting discount) to be $           .
 
     OneSource and the selling stockholders have agreed to indemnify the
Underwriters and their controlling persons against certain liabilities,
including liabilities under the Securities Act.
 
     OneSource and certain stockholders of OneSource have agreed not to sell or
transfer any shares of common stock, or to engage in certain hedging
transactions with respect to the common stock, for a period of 180 days from the
date of this prospectus without the consent of William Blair, except in certain
limited circumstances. Stockholders who have agreed to this lock-up arrangement
hold an aggregate of                 shares of common stock and options to
purchase                 shares of common stock. For more information, see
"Shares Eligible for Future Sale."
 
     In connection with this offering, the Underwriters and other persons
participating in this offering may engage in transactions which affect the
market price of the common stock. These may include stabilizing and
over-allotment transactions and purchases to cover syndicate short positions.
Stabilizing transactions consist of bids or purchases for the purpose of
pegging, fixing or maintaining the price of the common stock. Over-allotment
involves selling more shares of common stock in this offering than are specified
on the cover page of this prospectus, which results in a syndicate short
position. The Underwriters may cover this short position by purchasing common
stock in the open market or by exercising all or part of their over-allotment
option. In addition, the representatives of the Underwriters may impose a
penalty bid. This allows the representatives to reclaim the selling concession
allowed to an Underwriter or selling group member if common stock sold by such
Underwriter or selling group member in this offering is repurchased by the
representatives in stabilizing or syndicate short covering transactions. These
transactions, which may be effected on the Nasdaq National Market, may
stabilize, maintain or otherwise affect the market price of the common stock and
could cause the price to be higher than it would be without these transactions.
The Underwriters and other participants in this offering are not required to
engage in any of these activities and may discontinue any of these activities at
any time without notice. Neither OneSource nor any of the Underwriters makes any
representation or prediction as to whether the Underwriters will engage in such
transactions or choose to discontinue any transactions engaged in or as to the
direction or magnitude of any effect that these transactions may have on the
price of the common stock.
 
     The representatives of the Underwriters have advised OneSource and the
selling stockholders that the Underwriters do not intend to confirm, without
client authorization, sales to any account over which they exercise
discretionary authority.
 
                                       58
60
 
     Prior to this offering, there has been no public market for OneSource's
common stock. Consequently, OneSource, representatives of the selling
stockholders and the representatives of the Underwriters negotiated to determine
the initial public offering price. They considered current market conditions,
OneSource's operating results in recent periods, the market capitalization of
other companies in its industry, estimates of OneSource's potential and other
factors they deemed relevant. The estimated price range specified on the cover
page of this prospectus may change because of market conditions and other
factors.
 
     The Underwriters have reserved for sale, at the initial public offering
price, up to 5% of the shares of common stock in this offering for OneSource
employees and certain other individuals with a relationship with OneSource.
Purchases of the reserved shares would reduce the number of shares available for
sale to the general public. The Underwriters will offer any reserved shares
which are not so purchased to the general public on the same terms as the other
shares.
 
     OneSource intends to apply for quotation of the common stock on the Nasdaq
National Market under the symbol "ONES."
 
     Certain of the Underwriters and their affiliates engage in transactions
with, and perform services for, OneSource in the ordinary course of business and
have engaged, and may in the future engage, in commercial banking and investment
banking transactions with OneSource. In connection with rendering such services
in the past, the Underwriters and their affiliates have received customary
compensation.
 
     William Blair is an affiliate of William Blair Venture Partners. As such,
William Blair may be deemed to be an affiliate of OneSource under Schedule E of
the By-Laws of the National Association of Securities Dealers, Inc. ("NASD").
Mr. Newmark, a principal of William Blair, currently serves on OneSource's Board
of Directors as the representative of William Blair Venture Partners. In
addition, since 1993, OneSource has paid William Blair Venture Partners an
annual management fee of $100,000 pursuant to an oral arrangement and OneSource
will pay William Blair Venture Partners $500,000 upon the closing of this
offering in termination of this arrangement. For more information, see
"Principal and Selling Stockholders" and "Certain Transactions." When an NASD
member participates in an offering of an affiliated company's equity securities,
Rule 2720 of the NASD requires that a "qualified independent underwriter" within
the meaning of the Rule participate in the preparation of the registration
statement and prospectus for the offering and conduct due diligence as part of
such preparation. In addition, if a bona fide independent market does not exist
for the offered securities, the public offering price can be no higher than that
recommended by the qualified independent underwriter. U.S. Bancorp Piper Jaffray
Inc. has accepted the responsibility of acting as the "qualified independent
underwriter" with respect to this offering and, accordingly, the initial public
offering price specified on the cover page of this prospectus does not exceed
that recommended by U.S. Bancorp Piper Jaffray in its capacity as such.
 
                                 LEGAL MATTERS
 
     The validity of the shares of common stock to be issued in this offering
will be passed upon for OneSource by Testa, Hurwitz & Thibeault, LLP, Boston,
Massachusetts. Certain legal matters in connection with this offering will be
passed upon for the Underwriters by Sidley & Austin, Chicago, Illinois.
 
                                       59
61
 
                                    EXPERTS
 
     The consolidated financial statements as of December 31, 1997 and 1998 and
for each of the three years in the period ended December 31, 1998 included in
this prospectus have been so included in reliance upon the report of
PricewaterhouseCoopers LLP, independent accountants, given on the authority of
said firm as experts in auditing and accounting.
 
                             ADDITIONAL INFORMATION
 
     OneSource has filed with the Commission a registration statement on Form
S-1 (including all amendments and exhibits thereto, the "Registration
Statement") under the Securities Act with respect to the common stock in this
offering. As permitted by the rules and regulations of the Commission, this
prospectus omits certain information contained in the Registration Statement.
For further information with respect to OneSource and the common stock offered
in this offering, you should refer to the Registration Statement and to the
exhibits and schedules filed as part thereof. Statements contained in this
prospectus regarding the contents of any agreement or other document filed as an
exhibit to the Registration Statement are not necessarily complete, and in each
instance reference is made to the copy of such agreement or document filed as an
exhibit to the Registration Statement, each such statement being qualified in
all respects by such reference. You may obtain copies of all or any portion of
the Registration Statement at prescribed rates from the public reference
facilities maintained by the Commission at Room 1024, Judiciary Plaza, 450 Fifth
Street, N.W., Washington, DC 20549, at its regional offices located at Seven
World Trade Center, New York, New York 10007 and 500 West Madison Street,
Chicago, Illinois 60661, or by calling the Commission at 1-800-SEC-0330. In
addition, the Commission maintains a Website that contains reports, proxy and
information statements and other information regarding registrants (including
OneSource) that file electronically with the Commission which can be accessed at
http://www.sec.gov.
 
     OneSource intends to furnish to its stockholders annual reports containing
consolidated financial statements audited by an independent public accounting
firm and with quarterly reports for each of the first quarters of each fiscal
year containing unaudited consolidated financial statements.
 
                                       60
62
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                   INDEX TO CONSOLIDATED FINANCIAL STATEMENTS
PAGE
                                                              ----
Report of Independent Accountants...........................  F-2
Consolidated Balance Sheet as of December 31, 1997 and 1998
  and Pro Forma December 31, 1998 (unaudited)...............  F-3
Consolidated Statement of Operations for the Years Ended
  December 31, 1996, 1997 and 1998..........................  F-4
Consolidated Statement of Changes in Stockholders' Deficit
  for the Years Ended December 31, 1996, 1997 and 1998......  F-5
Consolidated Statement of Cash Flows for the Years Ended
  December 31, 1996, 1997 and 1998..........................  F-6
Notes to Consolidated Financial Statements..................  F-7
F-1
63
 
                       REPORT OF INDEPENDENT ACCOUNTANTS
 
To the Board of Directors and Stockholders of
OneSource Information Services, Inc.
 
     In our opinion, the accompanying consolidated balance sheet and the related
consolidated statements of operations, of changes in stockholders' deficit and
of cash flows present fairly, in all material respects, the financial position
of OneSource Information Services, Inc. and its subsidiary at December 31, 1997
and 1998, and the results of their operations and their cash flows for each of
the three years in the period ended December 31, 1998 in conformity with
generally accepted accounting principles. These financial statements are the
responsibility of the Company's management; our responsibility is to express an
opinion on these financial statements based on our audits. We conducted our
audits of these statements in accordance with generally accepted auditing
standards which require that we plan and perform the audit to obtain reasonable
assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements, assessing the
accounting principles used and significant estimates made by management, and
evaluating the overall financial statement presentation. We believe that our
audits provide a reasonable basis for the opinion expressed above.
 
PRICEWATERHOUSECOOPERS LLP
 
Boston, Massachusetts
February 26, 1999
 
                                       F-2
64
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                           CONSOLIDATED BALANCE SHEET
                       (IN THOUSANDS, EXCEPT SHARE DATA)
DECEMBER 31,        PRO FORMA
                                                              -------------------   DECEMBER 31,
                                                                1997       1998         1998
                                                              --------   --------   ------------
                                                                                      (NOTE 2)
                                                                                    (UNAUDITED)
                              ASSETS
Current assets:
  Cash and cash equivalents.................................  $    341   $  8,665     $  8,665
  Accounts receivable, net of allowance for doubtful
     accounts of $210 and $300 at December 31, 1997 and
     1998, respectively.....................................     8,703      9,621        9,621
  Deferred subscription costs...............................     5,037      6,662        6,662
  Prepaid expenses and other current assets.................       323        426          426
                                                              --------   --------     --------
     Total current assets...................................    14,404     25,374       25,374
Property and equipment, net.................................     1,826      1,770        1,770
Restricted time deposit.....................................        --        100          100
Other assets................................................       414        402          402
                                                              --------   --------     --------
       Total assets.........................................  $ 16,644   $ 27,646     $ 27,646
                                                              ========   ========     ========
                LIABILITIES AND STOCKHOLDERS' DEFICIT
Current liabilities:
  Current portion of capital lease obligations..............  $    580   $    471     $    471
  Notes payable.............................................     1,530         --           --
  Accounts payable..........................................     1,204        995          995
  Accrued expenses..........................................     2,450      3,378        3,378
  Accrued royalties.........................................     2,684      4,626        4,626
  Deferred revenues.........................................    15,748     18,022       18,022
                                                              --------   --------     --------
     Total current liabilities..............................    24,196     27,492       27,492
Capital lease obligations...................................       439        233          233
Long-term debt..............................................     5,622      6,232        6,232
                                                              --------   --------     --------
       Total liabilities....................................    30,257     33,957       33,957
                                                              --------   --------     --------
Commitments (Note 13).......................................        --         --           --
Stockholders' deficit:
  Preferred stock, $0.01 par value:
     No shares authorized, issued or outstanding at December
     31, 1997 and 1998; 1,000,000 shares authorized, no
     shares issued and outstanding at December 31, 1998 on a
     pro forma basis (unaudited)............................        --         --           --
  Class P common stock, $0.01 par value:
     500,000 shares authorized, 352,800 and 352,400 shares
     issued and outstanding at December 31, 1997 and 1998,
     respectively, at issuance cost (liquidation preference
     $6,656); no shares authorized, issued and outstanding
     at December 31, 1998 on a pro forma basis
     (unaudited)............................................     3,528      3,524           --
  Common stock, $0.01 par value: 6,500,000, 6,500,000 and
     20,000,000 shares authorized; 3,284,992, 3,329,392,
            shares issued; and 3,234,592, 3,275,392, and
            shares outstanding, at December 31, 1997,
     December 31, 1998 and December 31, 1998 on a pro forma
     basis (unaudited), respectively........................        32         33
  Additional paid-in capital................................       397        759
  Unearned compensation.....................................        --        (39)         (39)
  Accumulated deficit.......................................   (17,432)   (10,444)     (10,444)
  Accumulated other comprehensive loss......................      (132)      (138)        (138)
  Common stock held in treasury, at cost....................        (6)        (6)          (6)
                                                              --------   --------     --------
       Total stockholders' deficit..........................   (13,613)    (6,311)      (6,311)
                                                              --------   --------     --------
       Total liabilities and stockholders' deficit..........  $ 16,644   $ 27,646     $ 27,646
                                                              ========   ========     ========
The accompanying notes are an integral part of these consolidated financial
                                  statements.

                                       F-3
65
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                      CONSOLIDATED STATEMENT OF OPERATIONS
                (IN THOUSANDS, EXCEPT SHARE AND PER SHARE DATA)
YEAR ENDED DECEMBER 31,
                                                        ----------------------------------------
                                                           1996          1997           1998
                                                        ----------    ----------    ------------
Revenues:
  Web-based product...................................  $       15    $    3,312     $   16,058
  CD Rom product......................................      30,419        27,072         14,370
                                                        ----------    ----------     ----------
                                                            30,434        30,384         30,428
                                                        ----------    ----------     ----------
Cost of revenues:
  Web-based product...................................         295         2,401          7,863
  CD Rom product......................................      12,244        10,444          5,792
                                                        ----------    ----------     ----------
                                                            12,539        12,845         13,655
                                                        ----------    ----------     ----------
  Gross profit........................................      17,895        17,539         16,773
                                                        ----------    ----------     ----------
Operating expenses:
  Selling and marketing...............................       8,572         9,167         11,577
  Platform and product development....................       7,252         6,375          6,313
  General and administrative..........................       3,664         3,401          3,847
                                                        ----------    ----------     ----------
     Total operating expenses.........................      19,488        18,943         21,737
                                                        ----------    ----------     ----------
     Loss from operations.............................      (1,593)       (1,404)        (4,964)
Interest expense......................................        (752)         (943)          (878)
Interest income.......................................          19            13            283
Gain on sale of product line..........................          --           501         12,797
                                                        ----------    ----------     ----------
     Income (loss) before income taxes and
       extraordinary gain.............................      (2,326)       (1,833)         7,238
Provision for income taxes............................          --            --            250
                                                        ----------    ----------     ----------
     Income (loss) before extraordinary gain..........      (2,326)       (1,833)         6,988
Extraordinary gain on early extinguishment of debt....         393            --             --
                                                        ----------    ----------     ----------
     Net income (loss)................................  $   (1,933)   $   (1,833)    $    6,988
Less: income attributable to Class P common stock.....         335           414          1,367
                                                        ----------    ----------     ----------
     Net income (loss) attributable to common stock...  $   (2,268)   $   (2,247)    $    5,621
                                                        ==========    ==========     ==========
Class P common stock:
  Basic and diluted earnings per share................  $     0.95    $     1.17     $     3.88
  Weighted average Class P common shares
     outstanding......................................     353,300       352,800        352,600
Common stock:
  Basic earnings (loss) per share.....................  $    (0.71)   $    (0.70)    $     1.72
  Diluted earnings (loss) per share...................  $    (0.71)   $    (0.70)    $     1.20
  Weighted average common shares outstanding:
     Basic............................................   3,187,695     3,216,385      3,263,309
     Diluted..........................................   3,187,695     3,216,385      4,699,337
Unaudited pro forma earnings per share:
  Basic...............................................                               $
  Diluted.............................................                               $
  Weighted average common shares outstanding:
     Basic............................................
     Diluted..........................................
The accompanying notes are an integral part of these consolidated financial
                                  statements.
                                       F-4
66
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
           CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' DEFICIT
                       (IN THOUSANDS, EXCEPT SHARE DATA)
CLASS P
                                   COMMON STOCK        COMMON STOCK      ADDITIONAL
                                 ----------------   ------------------    PAID-IN       UNEARNED     COMPREHENSIVE   ACCUMULATED
                                 SHARES    AMOUNT    SHARES     AMOUNT    CAPITAL     COMPENSATION   INCOME (LOSS)     DEFICIT
                                 -------   ------   ---------   ------   ----------   ------------   -------------   -----------
Balance, December 31, 1995.....  353,800   $3,538   3,225,600    $32        $376          $ --                        $(13,666)
Comprehensive loss:
 Net loss......................                                                                         $(1,933)        (1,933)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................                                                                            (130)
                                                                                                        -------
     Comprehensive loss........                                                                          (2,063)
                                                                                                        =======
Issuance of common stock
 pursuant to exercise of
 options.......................                        14,976     --           4
Reacquisition and retirement of
 Class P common stock..........   (1,000)    (10)
Reacquisition of common stock
 for treasury..................
                                 -------   ------   ---------    ---        ----          ----                        --------
Balance, December 31, 1996.....  352,800   3,528    3,240,576     32         380            --                         (15,599)
Comprehensive loss:
 Net loss......................                                                                          (1,833)        (1,833)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................                                                                              30
                                                                                                        -------
     Comprehensive loss........                                                                          (1,803)
                                                                                                        =======
Issuance of common stock
 pursuant to exercise of
 options.......................                        44,416     --          17
                                 -------   ------   ---------    ---        ----          ----                        --------
Balance, December 31, 1997.....  352,800   3,528    3,284,992     32         397            --                         (17,432)
Comprehensive income:
 Net income....................                                                                           6,988          6,988
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................                                                                              (6)
                                                                                                        -------
     Comprehensive income......                                                                         $ 6,982
                                                                                                        =======
Issuance of common stock
 pursuant to exercise of
 options.......................                        44,400      1          22
Unearned compensation relating
 to grants of stock options....                                               45           (45)
Compensation relating to grants
 of stock options..............                                                              6
Compensation relating to
 modification of stock options
 on sale of product line.......                                              295
Reacquisition and retirement of
 Class P common stock..........     (400)     (4)
Reacquisition of common stock
 for treasury..................
                                 -------   ------   ---------    ---        ----          ----                        --------
Balance, December 31, 1998.....  352,400   $3,524   3,329,392    $33        $759          $(39)                       $(10,444)
                                 =======   ======   =========    ===        ====          ====                        ========
ACCUMULATED
                                     OTHER       TREASURY STOCK        TOTAL
                                 COMPREHENSIVE   ---------------   STOCKHOLDERS'
                                     LOSS        SHARES   AMOUNT      DEFICIT
                                 -------------   ------   ------   -------------
Balance, December 31, 1995.....      $ (32)      41,400    $(5)      $ (9,757)
Comprehensive loss:
 Net loss......................                                        (1,933)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................       (130)                              (130)
     Comprehensive loss........
Issuance of common stock
 pursuant to exercise of
 options.......................                                             4
Reacquisition and retirement of
 Class P common stock..........                                           (10)
Reacquisition of common stock
 for treasury..................                   9,000     (1)            (1)
                                     -----       ------    ---       --------
Balance, December 31, 1996.....       (162)      50,400     (6)       (11,827)
Comprehensive loss:
 Net loss......................                                        (1,833)
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................         30                                 30
     Comprehensive loss........
Issuance of common stock
 pursuant to exercise of
 options.......................                                            17
                                     -----       ------    ---       --------
Balance, December 31, 1997.....       (132)      50,400     (6)       (13,613)
Comprehensive income:
 Net income....................                                         6,988
 Other comprehensive income
   (loss):
   Foreign currency translation
     adjustment................         (6)                                (6)
     Comprehensive income......
Issuance of common stock
 pursuant to exercise of
 options.......................                                            23
Unearned compensation relating
 to grants of stock options....                                            --
Compensation relating to grants
 of stock options..............                                             6
Compensation relating to
 modification of stock options
 on sale of product line.......                                           295
Reacquisition and retirement of
 Class P common stock..........                                            (4)
Reacquisition of common stock
 for treasury..................                   3,600     --             --
                                     -----       ------    ---       --------
Balance, December 31, 1998.....      $(138)      54,000    $(6)      $ (6,311)
                                     =====       ======    ===       ========
The accompanying notes are an integral part of these consolidated financial
                                  statements.
 
                                       F-5
67
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                      CONSOLIDATED STATEMENT OF CASH FLOWS
                                 (IN THOUSANDS)
YEAR ENDED DECEMBER 31,
                                                              ------------------------------
                                                               1996       1997        1998
                                                              -------    -------    --------
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS
Cash flows relating to operating activities
  Net income (loss).........................................  $(1,933)   $(1,833)   $  6,988
  Adjustments to reconcile net income (loss) to net cash
    provided (used) by operating activities:
    Depreciation and amortization...........................    2,670      1,776       1,518
    Compensation expense relating to grants of stock
       options..............................................       --         --           6
    Amortization of debt discount...........................      108        142         121
    Loss on sale leaseback transaction......................       --         --          45
    Gain on sale of product line............................       --       (501)    (12,797)
    Gain on early extinguishment of debt....................     (393)        --          --
    Changes in assets and liabilities:
       Accounts receivable..................................     (781)        17        (946)
       Deferred subscription costs..........................     (178)      (748)     (2,217)
       Prepaid expenses and other assets....................     (255)        14         (43)
       Accounts payable.....................................      509       (459)       (213)
       Accrued expenses.....................................      507        758       1,075
       Accrued royalties....................................       76       (128)      2,283
       Deferred revenues....................................      943        453       5,373
                                                              -------    -------    --------
    Net cash provided (used) by operating activities........    1,273       (509)      1,193
                                                              -------    -------    --------
Cash flows relating to investing activities
  Investment in certificate of deposit......................       --         --        (100)
  Purchases of property and equipment.......................   (1,332)      (878)     (1,252)
  Capitalization of software development costs..............     (300)       (75)       (200)
  Net proceeds from sale of product line....................       --        501      10,563
                                                              -------    -------    --------
    Net cash provided (used) by investing activities........   (1,632)      (452)      9,011
                                                              -------    -------    --------
Cash flows relating to financing activities
  Proceeds from issuance of common stock....................        4         17          23
  Repurchase of Class P common stock and common stock.......      (11)        --          (4)
  Net borrowings (repayments) under line of credit..........     (400)       883      (1,183)
  Borrowings under term loan................................      575         --          --
  Repayments of term loan...................................     (208)      (228)       (347)
  Proceeds from sale and leaseback of fixed assets..........      289        753         228
  Repayments of capital lease obligations...................     (402)      (607)       (684)
                                                              -------    -------    --------
    Net cash provided (used) by financing activities........     (153)       818      (1,967)
                                                              -------    -------    --------
Effect of exchange rate changes on cash and cash
  equivalents...............................................       81        (51)         87
                                                              -------    -------    --------
Increase (decrease) in cash and cash equivalents............     (431)      (194)      8,324
Cash and cash equivalents, beginning of year................      966        535         341
                                                              -------    -------    --------
Cash and cash equivalents, end of year......................  $   535    $   341    $  8,665
                                                              =======    =======    ========
Supplemental disclosure of cash flow information:
  Cash paid for interest....................................  $   218    $   301    $    209
  Cash paid for taxes.......................................       --         --         175
Supplemental disclosure of noncash investing and financing
  activities:
  Additions to capital lease obligations for purchases of
    fixed assets............................................  $   430    $    87    $    183
  Additions to capital lease obligations for sale and
    leaseback of fixed assets...............................      289        753         228
  Additions to long-term debt for accrued interest..........      440        480         489
  Exchange of property and equipment for the retirement of
    capital lease obligations...............................       --         --          41
The accompanying notes are an integral part of these consolidated financial
                                  statements.
                                       F-6
68
 
                      ONESOURCE INFORMATION SERVICES, INC.
 
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
 
1.  NATURE OF BUSINESS
 
     OneSource Information Services, Inc. and its wholly-owned subsidiary
provide Web-based business and financial information to professionals in
corporations and other enterprises. OneSource primarily sells its products
through a direct sales force located throughout the United States and United
Kingdom. OneSource manages its business as a single segment.
 
2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
PRINCIPLES OF CONSOLIDATION
 
     The consolidated financial statements include the accounts of OneSource
Information Services, Inc. and OneSource Information Services Limited, its
wholly-owned subsidiary (collectively, "OneSource"). All significant
intercompany transactions and balances have been eliminated.
 
REVENUE RECOGNITION
 
     OneSource's products are sold on a subscription basis pursuant to customer
contracts that span varying periods of time but are generally for a period of
one year. In accordance with its customer agreements, OneSource initially
records receivables and defers the related revenue at the time amounts are
billed to customers. Revenues are recognized ratably over the related
subscription period.
 
SUBSCRIPTION COSTS
 
     Subscription costs represent sales commission and royalty costs that are
directly associated with securing a subscription and procuring information to be
delivered over the subscription period, respectively. These costs are deferred
and amortized ratably over the associated subscription period as a component of
selling and marketing expense and cost of revenues, respectively. At December
31, 1997 and 1998, deferred subscription costs consisted of $1,365,000 and
$1,250,000, respectively, related to sales commissions and $3,672,000 and
$5,412,000, respectively, related to royalties.
 
CASH AND CASH EQUIVALENTS
 
     Cash equivalents consist of money market funds with original maturities of
three months or less and are stated at cost which approximates fair market
value. These funds are managed by a financial institution with a strong credit
rating. Accordingly, the investments are subject to minimal credit and market
risks.
 
PROPERTY AND EQUIPMENT
 
     Property and equipment are recorded at cost and depreciated over their
estimated useful lives, generally three to five years, using the straight-line
method. Equipment held under capital leases is stated at the fair value of the
equipment at inception of the leases and is amortized on a straight-line basis
over the term of the leases.
 
                                       F-7
69
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
PLATFORM AND PRODUCT DEVELOPMENT AND SOFTWARE DEVELOPMENT COSTS
 
     Platform and product development costs, other than certain software
development costs, are charged to expense as incurred. Software development
costs incurred subsequent to the establishment of technological feasibility, and
prior to general release of the product, are capitalized and amortized on a
straight-line basis over the estimated useful lives of the related products,
generally twenty-four to thirty-six months. For the years ended December 31,
1996, 1997 and 1998, amortization of capitalized software development costs
amounted to $340,000, $413,000 and $198,000, respectively.
 
FINANCIAL INSTRUMENTS
 
     Fair values of OneSource's financial instruments, which include cash and
cash equivalents, restricted time deposits, accounts receivable, long-term debt
and capital lease obligations are based on quoted market prices and assumptions
concerning the amount and timing of estimated future cash flows and assumed
discount rates reflecting varying degrees of perceived risk. The carrying value
of these financial instruments approximated their fair value at December 31,
1997 and 1998.
 
CONCENTRATION OF CREDIT RISK
 
     Concentration of credit risk with respect to accounts receivable is limited
due to the large number of companies comprising OneSource's client base. Ongoing
credit evaluations of customers' financial condition are performed and
collateral is generally not required. OneSource maintains reserves for potential
credit losses and such losses, in the aggregate, have not exceeded management's
expectations.
 
ACCOUNTING FOR STOCK-BASED COMPENSATION
 
     OneSource accounts for stock-based compensation to employees in accordance
with Accounting Principles Board Opinion ("APB") No. 25, "Accounting for Stock
Issued to Employees" and related interpretation. Accordingly, compensation
expense is recorded for options issued to employees in fixed amounts to the
extent that the fixed exercise prices are less than the fair market value of
OneSource's common stock at the date of grant. OneSource follows the disclosure
requirements of Statement of Financial Accounting Standards ("SFAS") No. 123,
"Accounting for Stock-Based Compensation" (Note 8). All stock-based awards to
non-employees are accounted for at their fair value in accordance with SFAS No.
123.
 
UNAUDITED PRO FORMA BALANCE SHEET
 
     Prior to the closing of OneSource's initial public offering, each
outstanding share of Class P common stock (the "Class P stock") will be
reclassified into one share of common stock plus an additional number of shares
of common stock (determined by dividing the preference amount for such share by
the assumed initial public offering price of $      per share). In addition,
upon the closing of OneSource's initial public offering, OneSource will file a
Restated Certificate of Incorporation which will authorize 1,000,000 shares of a
single class of undesignated preferred
 
                                       F-8
70
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
stock, $0.01 par value per share, will cancel authorization of the Class P
common stock and will have authorized 20,000,000 shares of common stock. This
reclassification and other changes have been reflected in the unaudited pro
forma balance sheet as of December 31, 1998.
 
EARNINGS PER SHARE AND UNAUDITED PRO FORMA EARNINGS PER SHARE
 
     Earnings per share is computed in accordance with SFAS No. 128, "Earnings
Per Share." SFAS No. 128 requires the presentation of two amounts, basic
earnings per share and diluted earnings per share. The two-class method of
computing earnings per share has been used since the Class P stock and the
common stock share ratably in earnings remaining subsequent to the 12% yield on
the Class P stock.
 
     Earnings per share of Class P stock is calculated by dividing the yield
earned and income (loss) attributable to Class P stock by the weighted average
number of shares of Class P stock outstanding during the period. Diluted
earnings per share is the same for all periods presented as there are no
securities outstanding that would result in dilution for Class P stock.
 
     Earnings per share of common stock is calculated by dividing income (loss)
attributable to common stock by the weighted average number of shares of common
stock outstanding during the period. Diluted earnings per share is calculated by
considering the impact of potential common stock as if they were converted into
common stock at the beginning of the period. Potential common stock equivalents
are not included in loss periods as they are anti-dilutive.
 
     Unaudited pro forma basic and diluted earnings per share of common stock
for the year ended December 31, 1998 have been calculated based on net income
applicable to all classes of common stock and assuming the reclassification of
OneSource's Class P common stock prior to the completion of this offering, as if
such reclassification had occurred at January 1, 1998. Each share of Class P
common stock will be reclassified into one share of common stock plus an
additional number of shares of common stock (determined by dividing the
preference amount for such share by the assumed initial public offering price of
$     per share).
 
FOREIGN CURRENCY TRANSLATION
 
     Assets and liabilities of OneSource's United Kingdom operations, where the
local currency is the functional currency, are translated into US dollars at the
exchange rate in effect as of the balance sheet date, while revenues and
expenses are translated at average exchange rates during the period. The
resultant translation adjustment is reflected as a separate component of
stockholders' deficit. Transaction gains and losses, which are not material in
amount, are reflected in the consolidated statement of operations.
 
USE OF ESTIMATES
 
     The preparation of financial statements in conformity with generally
accepted accounting principles requires OneSource management to make estimates
and assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the financial
statements and the reported amounts of revenues and expenses during the
reporting period. Actual results could differ from those estimates.

                                       F-9
71
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS
 
     In March 1998, the Accounting Standards Executive Committee ("AcSEC")
issued Statement of Position ("SOP") 98-1, "Accounting for the Costs of Computer
Software Developed or Obtained for Internal Use." SOP 98-1 establishes the
accounting for costs of software products developed or purchased for internal
use, including when such costs should be capitalized. OneSource does not expect
SOP 98-1, which is effective for OneSource beginning January 1, 1999, to have a
material effect on OneSource's financial condition or results of operations.
 
     In April 1998, the AcSEC issued SOP 98-5, "Reporting on the Costs of
Start-Up Activities." Start-up activities are defined broadly as those one-time
activities relating to opening a new facility, introducing a new product or
service, conducting business in a new territory, conducting business with a new
class of customer, commencing some new operation or organizing a new entity.
Under SOP 98-5, the cost of start-up activities should be expensed as incurred.
SOP 98-5 is effective for OneSource's calendar year 1999 financial statements
and OneSource does not expect its adoption to have a material effect on
OneSource's financial condition or results of operations.
 
     In June 1998, the Financial Accounting Standards Board issued SFAS No. 133,
"Accounting for Derivative Instruments and Hedging Activities." The new standard
establishes accounting and reporting standards for derivative instruments,
including certain derivative instruments embedded in other contracts, and for
hedging activities. SFAS No. 133 is effective for all fiscal quarters of fiscal
years beginning after June 15, 1999. OneSource does not expect SFAS No. 133 to
have a material effect on its financial condition or results of operations.
 
3.  PROPERTY AND EQUIPMENT
 
     Property and equipment consists of the following:
DECEMBER 31,
                                                  ------------------
                                                   1997       1998
                                                  -------    -------
                                                    (IN THOUSANDS)
Office and computer equipment...................  $ 5,222    $ 5,478
Furniture and fixtures..........................      293        326
                                                  -------    -------
                                                    5,515      5,804
Less: accumulated depreciation and
  amortization..................................   (3,689)    (4,034)
                                                  -------    -------
                                                  $ 1,826    $ 1,770
                                                  =======    =======
At December 31, 1997 and 1998, office and computer equipment under capital
leases totaled $2,112,000 and $1,304,000, respectively. Related accumulated
amortization of assets under capital leases totaled $1,158,000 and $702,000 at
December 31, 1997 and 1998, respectively. During the years ended December 31,
1996, 1997 and 1998, OneSource sold and leased back certain computer equipment
with net book values of $308,000, $788,000, and
 
                                      F-10
72
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
$237,000, respectively for cash proceeds of $289,000, $753,000 and $228,000.
During 1998, OneSource retired $525,000 of fully depreciated property and
equipment.
 
4.  BORROWINGS
 
NOTES PAYABLE
 
     OneSource entered into a credit agreement (the "Agreement") with a bank, as
amended, which provides for a line of credit (the "Line") of up to $2,500,000
through April 1, 1998 and a term loan (the "Term Loan") of $750,000 to be used
for financing equipment purchases. At December 31, 1997, borrowings under the
Line were $1,183,000 and borrowings under the Term Loan were $347,000. During
1998, the Line and the Term Loan expired and were repaid in full.
 
LONG-TERM DEBT
 
     In connection with the acquisition of the business in 1993, OneSource
entered into a subordinated note agreement with the seller with a face amount of
$5,000,000 (the "Note"). The Note bears interest at 8% per annum, payable
annually commencing March 31, 1995 and has been discounted to reflect the market
rate of 12% at the time of issuance. The initial discount totaling $938,000 is
being amortized to interest expense over the life of the Note using the
effective interest method. As of December 31, 1998, the unamortized discount was
$291,000. Interest payments may be added to the unpaid principal of the Note if
OneSource's cash flow, as defined in the Note agreement, is less than a
specified amount.
 
     The Note, and any accrued but unpaid interest thereon, is due on the
earlier of i) September 8, 2000, ii) the date OneSource's stockholders, in
connection with an acquisition, cease to own a majority of the capital stock of
OneSource, or iii) the date OneSource sells substantially all of its assets. In
the event OneSource issues equity securities with net proceeds to OneSource in
excess of $10,000,000, OneSource is required to make a prepayment of the
principal amount as defined in the Note agreement. The Note agreement requires
OneSource to comply with certain restrictive covenants, including the
maintenance of specified financial ratios, and restricts OneSource from paying
dividends.
 
     In December 1996, OneSource reached a settlement agreement for an alleged
breach by the seller of a provision of the Note agreement regarding the initial
acquisition of the business. Under the terms of the settlement, the seller
forgave $393,000, or $0.11 per common share, of the principal on the Note, which
amount has been recognized as an extraordinary gain on early extinguishment of
debt.
 
     As of December 31, 1998, the carrying value of the Note was $6,232,000. In
accordance with the terms of the Note agreement, OneSource has added $1,523,000
to the principal of the Note for interest which had accrued through the end of
December 31, 1997. Accrued interest related to the Note was $504,000 for the
year ended December 31, 1998 and, since OneSource met the cash flow requirements
set forth in the Note agreement, such amount is due by March 31, 1999.
 
                                      F-11
73
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
5.  EARNINGS PER SHARE
 
     The following tables set forth the computation of earnings per share of
common stock and Class P stock from net income (loss):
YEAR ENDED DECEMBER 31,
                                           -----------------------------------
                                             1996         1997         1998
                                           ---------    ---------    ---------
Numerator for common stock (in
  thousands):
  Net income (loss)......................  $  (1,933)   $  (1,833)   $   6,988
  Less: income attributable to Class P
     stock...............................        335          414        1,367
                                           ---------    ---------    ---------
                                           $  (2,268)   $  (2,247)   $   5,621
                                           =========    =========    =========
Denominator for common stock:
  Weighted average shares outstanding
     used for basic earnings per share...  3,187,695    3,216,385    3,263,309
Effect of dilutive securities:
  Stock options..........................         --           --    1,195,624
  Common stock warrants..................         --           --      240,404
                                           ---------    ---------    ---------
  Weighted average shares outstanding
     used for diluted earnings per
     share...............................  3,187,695    3,216,385    4,699,337
                                           =========    =========    =========
Total potential common equivalent shares consist of 1,743,448 stock options
outstanding with a weighted average exercise price of $2.91 per share and
240,404 common stock warrants exercisable at $0.12 per share as of December 31,
1998.
YEAR ENDED DECEMBER 31,
                                           -----------------------------------
                                             1996         1997         1998
                                           ---------    ---------    ---------
                                                     (IN THOUSANDS)
Numerator for Class P stock:
  Yield earned by Class P stock..........  $     586    $     660    $     742
  Income (loss) attributable to Class P
     stock...............................       (251)        (246)         625
                                           ---------    ---------    ---------
                                           $     335    $     414    $   1,367
                                           =========    =========    =========
Basic and diluted earnings per share of Class P stock are the same for all
periods presented since there are no potentially dilutive securities.
 
6.  CLASS P COMMON STOCK AND COMMON STOCK
 
     In connection with its initial capitalization, OneSource issued 356,400
shares of Class P stock and 3,207,600 shares of common stock at $10.00 per share
and $0.12 per share, respectively. The holders of the Class P stock, as a
separate class, are entitled to receive first all or a portion of any
distribution, as defined, until the "preference amount" and the original
 
                                      F-12
74
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
issuance cost has been paid in full. The preference amount is 12% compounded
quarterly. After all such payments have been made, the holders of the Class P
stock and of the common stock shall share pro rata in the remaining portion of
the distribution, as a single class. As of December 31, 1998, no dividends on
either the Class P stock or the common stock have been declared or paid, and no
payments of the aggregate yield have been made to the Class P stockholders. As a
result, the Class P stock is stated at its original issuance cost of $10.00 per
share. As of December 31, 1998, the liquidation preference of these shares was
$6,656,000.
 
     All holders of Class P stock and all holders of common stock are entitled
to one vote per share on all matters to be voted upon by OneSource's
stockholders. The Class P stock is not convertible into common stock without the
prior agreement of the Class P stockholders and OneSource.
 
7.  WARRANTS
 
     In connection with the Note agreement (Note 4), OneSource issued a warrant
exercisable at $0.12 per share for 200,000 shares of OneSource's common stock.
The warrant is currently exercisable and expires on September 8, 2002. In
connection with the credit agreement (Note 4), OneSource also issued a warrant
to the Term Loan holder which entitles the holder to purchase 40,404 shares of
OneSource's common stock at $0.12 per share. The warrant is currently
exercisable and expires on the later of September 8, 2003 or five years from the
effective date of an initial public offering of OneSource's common stock. The
fair value of these warrants at the date of issuance was determined to be
$10,000 in the aggregate. OneSource has reserved 240,404 shares of common stock
for issuance upon exercise of the above warrants.
 
8.  STOCK PLANS
 
     The 1993 Stock Purchase and Option Plan (the "1993 Plan") provides for the
grant of incentive stock options and non-qualified stock options for the
purchase of up to an aggregate of 2,100,000 shares of OneSource's common stock
by employees, directors, consultants and advisors of OneSource. The Board of
Directors determines the term of each option, option price, number of shares for
which each option is granted, whether restrictions will be imposed on the shares
subject to options, and the vesting schedule of each option. The exercise price
for incentive stock options granted may not be less than the fair value per
share of the underlying common stock on the date granted as determined by the
Board of Directors (not less than 110% of the fair value for options granted to
holders of more than 10% of the voting stock of OneSource). Additionally, the
term of the options cannot exceed ten years (five years for options granted to
holders of more than 10% of the voting stock of OneSource). The options
generally vest over a four-year period.
 
     In February 1999, the Board of Directors of OneSource approved the 1999
Stock Option and Incentive Plan (the "1999 Stock Option Plan") to be effective
upon the closing of OneSource's initial public offering. The 1999 Stock Option
Plan provides for the grant of stock-based awards to employees, officers and
directors of, and consultants or advisors to,
 
                                      F-13
75
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
OneSource. A total of 800,000 shares of common stock are authorized for issuance
upon the exercise of options or other awards granted under the 1999 Stock Option
Plan.
 
     In February 1999, the Board of Directors of OneSource approved the 1999
Employee Stock Purchase Plan (the "1999 Purchase Plan"), to be effective upon
the closing of OneSource's initial public offering. The 1999 Purchase Plan
provides for the issuance of a maximum of 100,000 shares of common stock.
 
     Transactions under the 1993 Plan during the years ended December 31, 1996,
1997 and 1998 are summarized as follows:
WEIGHTED-
                                               NUMBER OF       AVERAGE
                                                SHARES      EXERCISE PRICE
                                               ---------    --------------
Outstanding--December 31, 1995...............  1,382,756        $2.17
  Granted (weighted average fair value of
     $0.25)..................................    620,700         3.53
  Exercised..................................    (14,976)        0.25
  Forfeited..................................    (85,876)        1.39
                                               ---------
Outstanding--December 31, 1996...............  1,902,604         2.67
  Granted (weighted average fair value of
     $0.25)..................................    144,600         3.52
  Exercised..................................    (44,416)        0.39
  Forfeited..................................   (230,540)        2.99
                                               ---------
Outstanding--December 31, 1997...............  1,772,248         2.75
  Granted (weighted average fair value of
     $1.66)..................................    100,700         4.44
  Exercised..................................    (44,400)        0.55
  Forfeited..................................    (85,100)        2.73
                                               ---------
Outstanding--December 31, 1998...............  1,743,448         2.91
                                               =========
The following table summarizes information about stock options outstanding
at December 31, 1998:
WEIGHTED-
                                                     AVERAGE
                                                    REMAINING       NUMBER OF
                                      NUMBER       CONTRACTUAL       OPTIONS
EXERCISE PRICE                      OF OPTIONS    LIFE IN YEARS    EXERCISABLE
--------------                      ----------    -------------    -----------
$0.25.............................    370,548          4.9            365,973
 2.78.............................    675,900          6.4            496,950
 4.45.............................    697,000          6.7            478,825
                                    ---------                       ---------
                                    1,743,448          6.2          1,341,748
                                    =========                       =========
F-14
76
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     As of December 31, 1996 and 1997, 925,853 and 1,214,860 options were
exercisable, respectively, under the 1993 Plan. As of December 31, 1998, there
were 252,760 shares of common stock available for grant to employees under the
1993 Plan.
 
     The fair value of each option grant is estimated on the date of grant using
the minimum value method with the following assumptions for grants in 1996, 1997
and 1998: dividend yield of 0.0% for all years; risk-free interest rates of
6.4%, 6.2% and 5.2% for 1996, 1997 and 1998, respectively; and a
weighted-average expected option term of 5 years for all years.
 
     Compensation expense has been recognized for OneSource's stock option plan
under APB No. 25. Had compensation cost been determined based on the fair value
of the options at the grant date consistent with the provisions of SFAS No. 123,
OneSource's net income (loss) and earnings (loss) per share would have been
increased to the pro forma amounts indicated below:
YEAR ENDED DECEMBER 31,
                                                 ----------------------------
                                                  1996       1997       1998
                                                 -------    -------    ------
Net income (loss) (in thousands):
  As reported..................................  $(1,933)   $(1,833)   $6,988
  Pro-forma....................................   (2,006)    (1,890)    6,909
Basic and diluted earnings per Class P common
  share:
  As reported..................................     0.95       1.17      3.88
  Pro-forma....................................     0.92       1.15      3.85
Basic earnings per common share:
  As reported..................................    (0.71)     (0.70)     1.72
  Pro-forma....................................    (0.73)     (0.71)     1.70
Diluted earnings per common share:
  As reported..................................    (0.71)     (0.70)     1.20
  Pro-forma....................................    (0.73)     (0.71)     1.18
Because options vest over several years and additional option grants are
expected to be made in future years, results of operations for future years may
be materially different if the provisions of SFAS No. 123 are applied.
 
     In conjunction with the sale of the CD-Insurance division, OneSource
modified the terms of 111,352 stock options held by terminated employees. In
accordance with APB No. 25, compensation expense of $295,000 was recorded as a
reduction of the gain on the sale of the insurance division in the year ended
December 31, 1998.
 
     During 1998, 99,800 stock options were granted with an exercise price of
$4.45 per share and 900 stock options were granted with an exercise price of
$2.78 per share; these exercise prices were below the estimated fair market
value of the common stock at the date of grant. Unearned compensation of $45,000
was recorded, in accordance with APB No. 25, and will be amortized over the
related vesting period. Compensation expense of $6,000 was recorded in the
 
                                      F-15
77
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
year ended December 31, 1998. Options issued during 1996 and 1997 were granted
with exercise prices above the estimated fair market value of the common stock
at the date of grant.
 
9.  INCOME TAXES
 
     Components of the income (loss) before income taxes and extraordinary gain
and of the current provision for income taxes are as follows:
YEAR ENDED DECEMBER 31,
                                                 ----------------------------
                                                  1996       1997       1998
                                                 -------    -------    ------
                                                        (IN THOUSANDS)
Income (loss) before income taxes and
  extraordinary gain:
  Domestic.....................................  $(1,976)   $(2,124)   $7,204
  Foreign......................................     (350)       291        34
                                                 -------    -------    ------
                                                 $(2,326)   $(1,833)   $7,238
                                                 =======    =======    ======
Current provision for income taxes:
  Federal......................................  $    --    $    --    $  200
  State........................................       --         --        45
  Foreign......................................       --         --         5
                                                 -------    -------    ------
                                                 $    --    $    --    $  250
                                                 =======    =======    ======
OneSource had no deferred provision for income taxes in each of the years
ended December 31, 1996, 1997 and 1998 due to the offsetting effects of the
valuation allowance on its net deferred tax assets. There was no income tax
effect related to the extraordinary gain on early extinguishment of debt in
1996. Provision has not been made for US or additional foreign taxes on
undistributed earnings of foreign subsidiaries as those earnings have been
permanently reinvested. Such taxes, if any, are not expected to be significant.
 
                                      F-16
78
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     Income taxes computed using the federal statutory income tax rate differ
from OneSource's effective tax rate primarily due to the following:
YEAR ENDED DECEMBER 31,
                                                   -------------------------
                                                   1996     1997      1998
                                                   -----    -----    -------
                                                        (IN THOUSANDS)
Income tax expense (benefit) at US federal
  statutory tax rate.............................  $(657)   $(623)   $ 2,461
State income taxes, net of federal tax effect....   (115)    (125)       508
Permanent items..................................     79       20         21
Other............................................     20       (4)        36
Change in deferred tax asset valuation
  allowance......................................    673      732     (2,776)
                                                   -----    -----    -------
Provision for income taxes.......................  $  --    $  --    $   250
                                                   =====    =====    =======
Components of OneSource's deferred tax assets and liabilities are as
follows:
DECEMBER 31,
                                                  ------------------
                                                   1997       1998
                                                  -------    -------
                                                    (IN THOUSANDS)
Deferred tax assets:
  Net operating loss carryforwards..............  $ 3,394    $   238
  Depreciation..................................      378        537
  Accrued expenses..............................      222        623
  Deferred revenues.............................    2,159      1,342
  Equity compensation...........................       --        123
  Miscellaneous.................................      120        133
                                                  -------    -------
     Gross deferred tax asset...................    6,273      2,996
  Less: valuation allowance.....................   (4,544)    (1,768)
                                                  -------    -------
     Total deferred tax assets..................    1,729      1,228
                                                  -------    -------
Deferred tax liabilities:
  Prepaid expenses..............................    1,068        513
  Deferred royalties............................      253        252
  Amortization of debt discount.................      163        217
  Capitalized software development costs........      126        127
  Tax operating leases..........................      119        119
                                                  -------    -------
     Total deferred tax liabilities.............    1,729      1,228
                                                  -------    -------
Net deferred tax assets.........................  $    --    $    --
                                                  =======    =======
F-17
79
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     Realization of OneSource's net deferred tax assets is contingent upon the
generation of future taxable income. Due to the uncertainty of realization of
these tax benefits, OneSource has provided a valuation allowance for the full
amount of its net deferred tax assets.
 
     During 1998, OneSource utilized $8,000,000 of net operating loss
carryforwards. At December 31, 1998, OneSource had net operating loss
carryforwards of $575,000 for foreign tax purposes which do not expire. Under
the provisions of the Internal Revenue Code, if certain substantial changes in
OneSource's ownership should occur, the amount of net operating loss
carryforwards which could be utilized annually to offset future taxable income
and income tax liability may be limited. The amount of any annual limitation is
determined based upon OneSource's value prior to an ownership change.
 
10.  SALE OF PRODUCT LINES
 
     In June 1997, OneSource sold its CD Rom banking product line for $650,000
in cash. In connection with the sale, OneSource entered a non-compete agreement
for five years. As a result of the sale, OneSource recorded a gain of $501,000
which is net of expenses of $149,000 incurred in conjunction with the sale. No
assets or liabilities with recorded net book values were transferred in
connection with this product line sale.
 
     In May 1998, OneSource sold its CD-Insurance division for $11,000,000 in
cash and entered a software license agreement for $4,000,000 to be received in
equal quarterly installments for two years commencing January 1, 1999. In
connection with the sale, OneSource also entered a non-compete agreement for
five years. As a result of the sale, OneSource recorded a gain of $12,797,000
which includes: (i) the recognition of $3,124,000 of deferred revenues and
$595,000 of deferred subscription costs based upon the assumption by the buyer
of all obligations to service the existing subscriber base of the insurance
division, (ii) $530,000 of employee severance costs and (iii) $202,000 of
expenses associated with the sale. Payments pertaining to the software license
agreement will be recognized in other income as support services are performed
and payments become due in accordance with the agreement.
 
11.  EMPLOYEE BENEFIT PLANS
 
     After three months of service, OneSource employees are eligible to
participate in a tax deferred savings plan (the "Savings Plan") under Section
401(k) of the Internal Revenue Code. OneSource matches 25% of the first 6%
contributed by the employee, and the employee becomes fully vested in
OneSource's matching contribution after three years of service. OneSource's
contributions to the Savings Plan totaled $122,000, $116,000 and $120,000 for
the years ended December 31, 1996, 1997 and 1998, respectively.
 
12.  RELATED PARTY TRANSACTIONS
 
     At December 31, 1997 and 1998, OneSource had accounts receivable of
$117,000 and $335,000, respectively, due from two stockholders. OneSource
recognized revenue of $200,000, $292,000 and $318,000 in the years ended
December 31, 1996, 1997, and 1998 respectively, from these parties.
 
                                      F-18
80
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
     Management fees paid to a stockholder and an affiliate of another
stockholder totaling $200,000 for each of the years ended December 31, 1996,
1997 and 1998 are included in general and administrative expenses.
 
13.  COMMITMENTS
 
  Leases
 
     OneSource leases facilities and certain equipment under various
noncancellable operating lease agreements. Total rent expense under such leases
was $1,271,000, $1,191,000 and $1,146,000 for the years ended December 31, 1996,
1997, and 1998, respectively. Future minimum lease commitments under all
noncancellable capital and operating leases at December 31, 1998 are as follows:
CAPITAL    OPERATING
                                                     LEASES      LEASES
                                                     -------    ---------
                                                        (IN THOUSANDS)
1999...............................................   $490       $  920
2000...............................................    207          231
2001...............................................     80          223
2002...............................................     --          221
2003...............................................     --           68
                                                      ----       ------
Total minimum lease payments.......................    777       $1,663
                                                                 ======
Less: amount representing interest.................     73
                                                      ----
Present value of net minimum lease payments,
  including current maturities of $471.............   $704
                                                      ====
In January 1999, OneSource entered into a five-year noncancellable
operating lease for a new operating facility. Minimum yearly rental payments
will be $655,000, commencing in June 1999. Pursuant to the lease, OneSource
entered into a $415,000 irrevocable letter of credit collateralized by a
certificate of deposit.
 
  Restricted Time Deposit
 
     In connection with a facility lease, OneSource is required to maintain, on
behalf of the landlord, an irrevocable letter of credit with a bank in the
amount of $100,000 over the term of the lease. In addition, OneSource was
required to maintain a certificate of deposit in an equal amount as security for
the letter of credit.
 
                                      F-19
81
                      ONESOURCE INFORMATION SERVICES, INC.
 
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(CONTINUED)
 
14.  GEOGRAPHIC INFORMATION
 
     Revenue was distributed geographically as follows:
YEAR ENDED DECEMBER 31,
                                        -----------------------------
                                         1996       1997       1998
                                        -------    -------    -------
                                               (IN THOUSANDS)
United States.........................  $25,294    $24,193    $23,428
United Kingdom........................    5,140      6,191      7,000
                                        -------    -------    -------
                                        $30,434    $30,384    $30,428
                                        =======    =======    =======
Substantially all of OneSource's identifiable assets are located in the
United States.
 
                                      F-20
82
 
     [The graphic contains the OneSource logo in the center of the page. Reading
from the top right diagonally to the bottom left of the page is the following
text: Turning World Class Information into Integrated Solutions For Demanding
Business Professionals Worldwide. The top left of the page depicts the names and
logos of the following OneSource information providers: The Investext Group;
Market Guide; Standard & Poor's; Comtex; Financial Times; Corp Tech; WorldScope
Disclosure; Hoover's Inc.; Reuters; and Dun & Bradstreet. The bottom half of the
page depicts the following OneSource customers by name and logo displayed
according to the following industry sectors noted in the text:
 
  Financial Institutions:
 
     Credit Suisse; Merrill Lynch; American Express: Bank of America.
 
  Professional Services:
 
     Bain & Company; KMPG; Deloitte Touche Tohmatsu; Ernst & Young.
 
  High Tech:
 
     Oracle; SAP; Platinum; IBM.
 
  Leading Corporations:
 
     Boeing; MCI Worldcom; BT; Nortel Networks.]
83
 
------------------------------------------------------
------------------------------------------------------
 
     YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS. WE
HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION DIFFERENT FROM THAT
WHICH IS SET FORTH IN THIS PROSPECTUS. WE ARE OFFERING TO SELL SHARES OF COMMON
STOCK AND SEEKING OFFERS TO BUY SHARES OF COMMON STOCK ONLY IN JURISDICTIONS
WHERE OFFERS AND SALES ARE PERMITTED. THE INFORMATION CONTAINED IN THIS
PROSPECTUS IS ACCURATE ONLY AS OF THE DATE OF THIS PROSPECTUS, REGARDLESS OF THE
TIME OF DELIVERY OF THE PROSPECTUS OR OF ANY SALE OF COMMON STOCK.
 
                          ---------------------------
 
                               TABLE OF CONTENTS
PAGE
                                     ----
Prospectus Summary.................    3
Risk Factors.......................    7
Reclassification...................   14
Use of Proceeds....................   15
Dividend Policy....................   15
Capitalization.....................   16
Dilution...........................   17
Selected Consolidated Financial
  Data.............................   18
Management's Discussion and
  Analysis of Financial Condition
  and Results of Operations........   20
Business...........................   32
Management.........................   43
Certain Transactions...............   49
Principal and Selling
  Stockholders.....................   50
Description of Capital Stock.......   51
Shares Eligible for Future Sale....   54
Underwriting.......................   57
Legal Matters......................   59
Experts............................   60
Additional Information.............   60
Index to Consolidated Financial
  Statements.......................  F-1
---------------------------
 
     Until              , 1999 (25 days after the date of this prospectus), all
dealers that effect transactions in these securities, whether or not
participating in this offering, may be required to deliver a prospectus. This is
in addition to the dealer's obligation to deliver a prospectus when acting as
underwriters and with respect to their unsold allotments or subscriptions.
------------------------------------------------------
------------------------------------------------------
------------------------------------------------------
------------------------------------------------------
 
                                               SHARES
 
                               [ONE SOURCE LOGO]
 
                                  COMMON STOCK
 

                            ------------------------
 
                                   PROSPECTUS
                                            , 1999
 
                            ------------------------

                            WILLIAM BLAIR & COMPANY
                         U.S. BANCORP PIPER JAFFRAY INC.
                          ADAMS, HARKNESS & HILL, INC.
 
------------------------------------------------------
------------------------------------------------------
84
 
                                    PART II
 
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 13.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.
 
     Estimated expenses payable in connection with the sale of the common stock
in this offering are as follows:
SEC registration fee........................................  $ 11,259
NASD filing fee.............................................     4,550
Nasdaq National Market listing fee..........................    49,000
Printing and engraving expenses.............................   125,000
Legal fees and expenses.....................................   250,000
Accounting fees and expenses................................         *
Transfer agent and registrar fees and expenses..............         *
Miscellaneous...............................................         *
                                                              --------
     Total..................................................  $      *
                                                              ========
------------
 
* To be completed by amendment
 
     OneSource will bear all of the expenses shown above.
 
ITEM 14.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
     The Delaware General Corporation Law, the Company's charter and by-laws
provide for indemnification of the Company's directors and officers for
liabilities and expenses that they may incur in such capacities. In general,
directors and officers are indemnified with respect to actions taken in good
faith in a manner reasonably believed to be in, or not opposed to, the best
interests of the Company, and with respect to any criminal action or proceeding,
actions that the indemnitee had no reasonable cause to believe were unlawful.
Reference is made to the Company's corporate charter and by-laws filed as
Exhibits 3.01 and 3.02 hereto, respectively.
 
     The Underwriting Agreement provides that the Underwriters are obligated,
under certain circumstances, to indemnify directors, officers and controlling
persons of the Company against certain liabilities, including liabilities under
the Securities Act. Reference is made to the form of Underwriting Agreement
filed as Exhibit 1.01 hereto.
 
     The Company intends to apply for a directors' and officers' insurance
policy.
 
ITEM 15.  RECENT SALES OF UNREGISTERED SECURITIES.
 
     In the three years preceding the filing of this registration statement, the
Company has issued the following securities that were not registered under the
Securities Act:
 
     Since January 1, 1996, the Company has issued options to purchase an
aggregate of 1,063,100 shares of common stock under the 1993 Plan, exercisable
at a weighted average price of $6.29 per share. From January 1, 1996 through
December 31, 1998, options to purchase 103,792 shares had been exercised. The
following table lists options granted between January 1, 1996 and March 1, 1999.
DATE                                                          SHARES     PRICE
----                                                          ------     -----
November 12, 1996...........................................  340,700    $2.78
November 12, 1996...........................................  280,000     4.45
April 17, 1997..............................................      600     2.78
July 17, 1997...............................................    1,000     2.78
II-1
85
DATE                                                          SHARES     PRICE
----                                                          ------     -----
October 16, 1997............................................    1,000     2.78
November 12, 1997...........................................    8,000     2.78
November 17, 1997...........................................   70,000     2.78
November 17, 1997...........................................   64,000     4.45
May 6, 1998.................................................      900     2.78
May 6, 1998.................................................   99,800     4.45
February 26, 1999...........................................   20,000     4.45
February 26, 1999...........................................   15,000    12.00
February 26, 1999...........................................  162,100    20.20
No underwriters were involved in the foregoing sales of securities. Such
sales were made in reliance upon the exemption provided by Section 4(2) of the
Securities Act for transactions not involving a public offering and/or Rule 701
under the Securities Act.
 
ITEM 16.  EXHIBITS AND FINANCIAL STATEMENT SCHEDULES.
 
  (a) EXHIBITS:
EXHIBIT
    NO.                               EXHIBIT
  -------                             -------
+1.01    Form of Underwriting Agreement
   +3.01    Form of Restated Certificate of Incorporation of the Company
    3.02    Amended and Restated Certificate of Incorporation of the
            Company
    3.03    By-laws, as amended and restated, of the Company
   +3.04    Second Amended and Restated By-Laws of the Company
   +4.01    Specimen certificate representing the common stock
   +5.01    Opinion of Testa, Hurwitz & Thibeault, LLP
   10.01    1993 Stock Purchase and Option Plan
  +10.02    1999 Stock Option and Incentive Plan
  +10.03    1999 Employee Stock Purchase Plan
   10.04    Registration Agreement dated September 8, 1993
   10.05    Stock Purchase Warrant issued to Lotus Development
            Corporation dated September 8, 1993
   10.06    Warrant Agreement with Silicon Valley Bank dated September
            8, 1993
   10.07    Subordinated Promissory Note issued to Lotus Development
            Corporation dated September 8, 1993
   10.08    Stock Purchase Agreement dated September 8, 1993
   10.09    Form of Management Stock Purchase Agreement
   10.10    Stock Purchase Agreement dated August 3, 1993, by and among
            Lotus Development Corporation, Datext, Inc. and Datext
            Holding Corporation
   10.11    Lease dated July 1, 1998 by and between OneSource and
            CambridgePark Two Limited Partnership
   10.12    Lease dated January 20, 1999 by and between OneSource and
            300 Baker Avenue Associates, Limited Partnership
   10.13    Agreement and Plan of Merger dated February 26, 1999 by and
            between OneSource Information Services, Inc. and OneSource
            Holding Corporation
  +10.14    Stockholders Agreement dated September 8, 1993
   21.01    Subsidiaries of the Company
   23.01    Consent of Testa, Hurwitz & Thibeault, LLP (included in
            Exhibit 5.01)
   23.02    Consent of PricewaterhouseCoopers LLP
II-2
86
EXHIBIT
    NO.                               EXHIBIT
  -------                             -------
24.01    Power of Attorney (included in signature page)
   27.01    Financial Data Schedule
------------
+ to be filed by amendment
 
  (b) FINANCIAL STATEMENT SCHEDULES:
 
     Schedule II -- Valuation and Qualifying Accounts
 
     All other schedules for which provision is made in the applicable
accounting regulations of the Securities and Exchange Commission are either not
applicable or the required information is included in the Consolidated Financial
Statements and Notes thereto, and therefore have been omitted.
 
ITEM 17.  UNDERTAKINGS.
 
     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers and controlling persons of the Company
pursuant to provisions described in Item 14 above, or otherwise, the Company has
been advised that in the opinion of the Securities and Exchange Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Company of expenses
incurred or paid by a director, officer or controlling person of the Company in
the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Company will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.
 
     The Company hereby undertakes: (1) to provide to the underwriters at the
closing specified in the underwriting agreement, certificates in such
denominations and registered in such names as required by the underwriters to
permit prompt delivery to each purchaser; (2) that for purposes of determining
any liability under the Securities Act, the information omitted from the form of
prospectus filed as part of a registration statement in reliance upon Rule 430A
and contained in the form of prospectus filed by the registrant pursuant to Rule
424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part
of this registration statement as of the time it was declared effective; and (3)
that for the purpose of determining any liability under the Securities Act, each
post-effective amendment that contains a form of prospectus shall be deemed to
be a new registration statement relating to the securities offered therein, and
the offering of such securities at that time shall be deemed to be the initial
bona fide offering thereof.
 
                                      II-3
87
 
                                   SIGNATURES
 
     Pursuant to the requirements of the Securities Act of 1933, the registrant
has duly caused this registration statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in Cambridge, Massachusetts on March 1,
1999.
 
                                          OneSource Information Services, Inc.
 
                                          By:     /s/ DANIEL J. SCHIMMEL
                                             -----------------------------------
                                             Daniel J. Schimmel
                                              President and Chief Executive
                                              Officer
 
                        POWER OF ATTORNEY AND SIGNATURES
 
     The undersigned officers and directors of OneSource Information Services,
Inc. hereby constitute and appoint Daniel J. Schimmel and Roy D. Landon, and
each of them singly, with full power of substitution, our true and lawful
attorneys-in-fact and agents to take any actions to enable OneSource Information
Services, Inc. to comply with the Securities Act, and any rules, regulations and
requirements of the Securities and Exchange Commission, in connection with this
registration statement, including the power and authority to sign for us in our
names in the capacities indicated below any and all amendments to this
registration statement and any other registration statement filed pursuant to
the provisions of Rule 462 under the Securities Act.
 
     Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.
SIGNATURE                                TITLE(S)                     DATE
                ---------                                --------                     ----
President and Chief Executive         March 1, 1999
                                            Officer and Director (principal
          /s/ DANIEL J. SCHIMMEL            executive officer)
------------------------------------------
            Daniel J. Schimmel
 
                                            Vice President, Finance and           March 1, 1999
                                            Administration (principal
            /s/ ROY D. LANDON               financial officer)
------------------------------------------
              Roy D. Landon
 
             /s/ MARTIN KAHN                Director                              March 1, 1999
------------------------------------------
               Martin Kahn
 
            /s/ DAVID DOMINIK               Director                              March 1, 1999
------------------------------------------
              David Dominik
 
            /s/ GREGG NEWMARK               Director                              March 1, 1999
------------------------------------------
              Gregg Newmark
II-4
88
 
                 SCHEDULE II--VALUATION AND QUALIFYING ACCOUNTS
 
                      ONESOURCE INFORMATION SERVICES, INC.
BALANCE AT
                                       BEGINNING OF    CHARGED TO                       BALANCE AT
DESCRIPTION                               PERIOD       OPERATIONS    DEDUCTIONS(1)     END OF PERIOD
-----------                            ------------    ----------    --------------    -------------
Year ended December 31, 1996
  Reserves and allowances deducted
     from asset accounts
     Allowance for doubtful
        accounts.....................    $161,000        49,000          49,000          $161,000
Year ended December 31, 1997
  Reserves and allowances deducted
     from asset accounts
     Allowance for doubtful
        accounts.....................    $161,000        72,000          23,000          $210,000
Year ended December 31, 1998
  Reserves and allowances deducted
     from asset accounts
     Allowance for doubtful
        accounts.....................    $210,000       120,000          30,000          $300,000
------------
(1) Doubtful accounts written off, net of recoveries
 
                                       S-1
89
 
                                 EXHIBIT INDEX
EXHIBIT
    NO.
  -------
+1.01    Form of Underwriting Agreement
   +3.01    Form of Restated Certificate of Incorporation of the Company
    3.02    Amended and Restated Certificate of Incorporation of the
            Company
    3.03    By-laws, as amended and restated, of the Company
   +3.04    Second Amended and Restated By-Laws of the Company
   +4.01    Specimen certificate representing the common stock
   +5.01    Opinion of Testa, Hurwitz & Thibeault, LLP
   10.01    1993 Stock Purchase and Option Plan
  +10.02    1999 Stock Option and Incentive Plan
  +10.03    1999 Employee Stock Purchase Plan
   10.04    Registration Agreement dated September 8, 1993
   10.05    Stock Purchase Warrant issued to Lotus Development
            Corporation dated September 8, 1993
   10.06    Warrant Agreement with Silicon Valley Bank dated September
            8, 1993
   10.07    Subordinated Promissory Note issued to Lotus Development
            Corporation dated September 8, 1993
   10.08    Stock Purchase Agreement dated September 8, 1993
   10.09    Form of Management Stock Purchase Agreement
   10.10    Stock Purchase Agreement dated August 3, 1993, by and among
            Lotus Development Corporation, Datext, Inc. and Datext
            Holding Corporation
   10.11    Lease dated July 1, 1998 by and between OneSource and
            CambridgePark Two Limited Partnership
   10.12    Lease dated January 20, 1999 by and between OneSource and
            300 Baker Avenue Associates, Limited Partnership
   10.13    Agreement and Plan of Merger dated February 26, 1999 by and
            between OneSource Information Services, Inc. and OneSource
            Holding Corporation
  +10.14    Stockholders Agreement dated September 8, 1993
   21.01    Subsidiaries of the Company
   23.01    Consent of Testa, Hurwitz & Thibeault, LLP (included in
            Exhibit 5.01)
   23.02    Consent of PricewaterhouseCoopers LLP
   24.01    Power of Attorney (included in signature page)
   27.01    Financial Data Schedule
------------
+ to be filed by amendment