QuickLinks -- Click here to rapidly navigate through this document

Commission File No.: 0-29954

FORM 6-K/A

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington DC 20549

Report of Foreign Issuer

Pursuant to Rule 13a-16 or 15d-16 of
the Securities Exchange Act of 1934

For the month of February 2003

THE THOMSON CORPORATION
(Translation of registrant's name into English)

Suite 2706, Toronto Dominion Bank Tower
P.O. Box 24, 66 Wellington St. West
Toronto-Dominion Centre
Toronto, Ontario
M5K 1A1, Canada
(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F o    Form 40-F ý

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes o    No ý

If "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82-.

EXHIBIT INDEX IS LOCATED AT PAGE 2 OF 12

1


Information furnished on this form:

Press Release dated February 26, 2003 of The Thomson Corporation entitled "Thomson Reports Full-Year and Fourth-Quarter 2002 Results".


EXHIBIT

Exhibit Number

   
  Page
1.   Press Release dated February 26, 2003.   4

2



SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

Certain statements contained in Exhibit number 1 constitute forward-looking statements, which are based on the Corporation's current expectations and assumptions, and are subject to a number of risks and uncertainties that could cause actual results to differ materially from those anticipated. Such risks and uncertainties include, among others, general business and economic conditions and competitive actions.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

    The Thomson Corporation
(Registrant)

Date: February 26, 2003

 

/s/  
PAULA R. MONAGHAN      
Assistant Secretary

3




QuickLinks

EXHIBIT
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
SIGNATURES

QuickLinks -- Click here to rapidly navigate through this document
The Thomson Corporation
Metro Center, One Station Place
Stamford, CT 06902
Tel (203) 969-8700 Fax (203) 977-8354
www.thomson.com
  LOGO

News Release

Investor Contact:

  Media Contact:

John Kechejian   Jason Stewart
Vice President, Investor Relations   Director, Public Relations
(203) 328-9470   (203) 328-8339
john.kechejian@thomson.com   jason.stewart@thomson.com

For Immediate Release


THOMSON REPORTS FULL-YEAR AND
FOURTH-QUARTER 2002 RESULTS


(Unless otherwise stated, all amounts are in US dollars)

STAMFORD, Conn. and TORONTO, February 26, 2003 — The Thomson Corporation (TSX: TOC; NYSE: TOC) today reported solid growth in revenues and earnings before interest, tax, depreciation, amortization and restructuring charges (EBITDA) for the year ended December 31, 2002.

Financial highlights for full-year 2002 include:


Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 2

        "We are very pleased with our performance in 2002, resulting from the successful execution of our strategic priorities," stated Richard J. Harrington, president and chief executive officer. "Under challenging market conditions, we achieved steady growth across Thomson as we brought several significant new products and services to market and effectively integrated our recent acquisitions. Going forward, we will continue to leverage the full depth, breadth and quality of Thomson offerings to provide market-leading customer solutions, drive efficiency, and deliver superior value to our shareholders."

Fourth-Quarter Results

        Revenue for the quarter was $2.2 billion, a 3% increase over the fourth quarter of 2001. Each Thomson market group expanded its margins significantly compared to the fourth quarter of 2001, increasing consolidated EBITDA 23% to $772 million. Earnings attributable to common shares were $283 million, or $0.44 per common share, for the fourth quarter of 2002, compared to $254 million, or $0.40 per common share, in the year-earlier period. Earnings for the fourth quarter of 2002 reflect the benefit from a new accounting standard eliminating amortization of goodwill. Fourth-quarter 2002 results also include a $22 million earnings benefit arising from the reversal of a valuation allowance with respect to the Corporation's principal UK pension plan, increasing reported earnings per share by $0.03.

        On a comparable accounting basis, and after adjusting for discontinued operations and one-time items, adjusted earnings from continuing operations for the fourth quarter of 2002 were $373 million, or $0.57 per common share, compared to $302 million, or $0.48 per common share, for the same period in 2001.

2002 Full-Year and Fourth-Quarter Business Highlights:


Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 3


Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 4

        Thomson Media revenues, which are reported within "corporate and other," declined 9% in 2002 to $201 million largely as a result of continued weakness in the advertising market. In 2002, EBITDA within the Media group more than doubled to $30 million as a result of a continued focus on restructuring and cost reduction programs.

        A non-cash charge of $67 million, net of tax, was included in the Corporation's fourth-quarter 2002 earnings reflecting its share of a write-down of goodwill recorded by Bell Globemedia Inc. (BGM). On February 7, 2003, Thomson announced it signed an agreement to sell its 20% interest in BGM to its principal shareholder, The Woodbridge Company Limited, for $279 million. Thomson will realize a gain from the sale of BGM, which is expected to close in March, largely offsetting the fourth quarter impairment charge.

        Beginning in the first quarter of 2003, Thomson will reflect stock option expense within its income statement and will restate prior periods. Accordingly, the expense will reflect the cost of all outstanding options, not just options granted in 2003. Stock option expense would have reduced reported basic earnings per share by $0.02 in 2002 and $0.01 in 2001.

Series V Preference Shares Redemption

        Thomson has exercised its right to redeem all of its outstanding Series V Cumulative Redeemable Preference Shares with a redemption date of April 14, 2003. The shares will be redeemed at a price of Cdn$25.50 in addition to any accrued and unpaid dividends up to, but not including, the redemption date. Currently, there are 18,000,000 outstanding Series V Preference Shares. Instructions regarding the receipt of the redemption amount are being mailed to registered holders of the Series V Preference Shares.

2003 Financial Outlook

        The Corporation's financial targets over the long term remain the achievement of average annual revenue growth between 7% and 9%, the expansion of EBITDA margins, and the improvement of its free cash flow generation. Early indications suggest that continued economic softness and market uncertainty will continue in 2003. In this environment the Corporation does not expect to achieve its long-term revenue growth targets in 2003. However, the Corporation anticipates that its overall revenues will continue to grow despite softness in some areas. EBITDA margins are expected to continue to expand and the Corporation will maintain its focus on driving free cash flow in 2003.

The Thomson Corporation

        The Thomson Corporation, with 2002 revenues of $7.8 billion, is a global leader in providing integrated information solutions to business and professional customers. Thomson provides value-added information, software tools and applications to more than 20 million users in the fields of law, tax, accounting, financial services, higher education, reference information, corporate training and assessment, scientific research and healthcare. The Corporation's common shares are listed on the Toronto and New York stock exchanges (TSX: TOC; NYSE: TOC).

- more -


Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 5

Note: The Thomson Corporation will webcast a discussion of full-year and fourth-quarter results beginning at 10:30 am EST today. To participate in the webcast, please visit www.thomson.com and click on the "Investor Relations" link located at the top of the page.

Note: Segmented results are presented on the basis of ongoing businesses, which exclude disposals. Disposals are businesses sold or held for sale, which do not qualify as discontinued operations. Discontinued operations include the results of our former newspaper operations. EBITDA, adjusted operating profit, free cash flow, adjusted earnings from continuing operations and related measures are used by Thomson to measure the Corporation's performance but do not have any standardized meaning prescribed by Canadian generally accepted accounting principles (GAAP) and therefore are unlikely to be comparable with the calculation of similar measures for other companies, and should not be viewed as alternatives to operating profit, net income, cash flow from operations or other measures of financial performance calculated in accordance with GAAP. We define and reconcile our EBITDA, adjusted operating profit and adjusted earnings from continuing operations to our income statement under GAAP, and we reconcile free cash flow to our cash flow statement under GAAP, in the following tables.

This news release, in particular the section under the heading "2003 Financial Outlook," includes forward-looking statements, which are based on certain assumptions and reflect the Corporation's current expectations. These forward-looking statements are subject to a number of risks and uncertainties that could cause actual results or events to differ materially from current expectations. Some of the factors that could cause actual results to differ materially from current expectations are: actions of our competitors; failure of our significant investments in technology to increase our revenues or decrease our operating costs; failure to fully derive anticipated benefits from our acquisitions; failure to develop additional products and services to meet our customers' needs, attract new customers or expand into new geographic markets; failure to meet the special challenges involved in expansion of our operations outside North America; failure to recruit and retain high quality management and key employees; consolidation of our customers; increased self-sufficiency of our customers; increased accessibility to free or relatively inexpensive information sources; failure to maintain the availability of information obtained through licensing arrangements and changes in the terms of our licensing arrangements; changes in the global economic conditions; inadequate protection of our intellectual property rights; an increase in our effective income tax rate; impairment loss affecting our goodwill and identifiable intangible assets recorded on our balance sheet; and failures or disruptions of our electronic delivery systems or the Internet. Additional factors are discussed in the Corporation's materials filed with the securities regulatory authorities in Canada and the United States from time to time. The Corporation disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

- more -


Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 6


CONSOLIDATED STATEMENT OF EARNINGS(1)
(millions of US dollars, except per common share data)

 
  Three Months Ended December 31
  Twelve Months Ended December 31
 
 
  2002
  2001
  2002
  2001
 
 
  (unaudited)

   
   
 
Revenues     2,190     2,128     7,756     7,237  
Cost of sales, selling, marketing, general and administrative expenses     (1,418 )   (1,499 )   (5,696 )   (5,451 )
Depreciation     (146 )   (119 )   (542 )   (476 )
Amortization     (72 )   (127 )   (288 )   (444 )
Restructuring charges         (10 )   (6 )   (30 )
   
 
 
 
 
Operating profit     554     373     1,224     836  
Net (losses) gains on disposals of businesses and investments     (28 )   3     (34 )   302  
Net interest expense and other financing costs     (72 )   (70 )   (291 )   (236 )
Income taxes     (103 )   (36 )   (192 )   (168 )
Equity in losses of associates     (72 )   (14 )   (101 )   (50 )
   
 
 
 
 
Earnings from continuing operations     279     256     606     684  
Earnings from discontinued operations     9     5     9     92  
   
 
 
 
 
Net earnings     288     261     615     776  
Dividends declared on preference shares     (5 )   (7 )   (19 )   (27 )
   
 
 
 
 
Earnings attributable to common shares     283     254     596     749  
   
 
 
 
 
Basic and fully diluted earnings per common share:                          
  — from continuing operations   $ 0.42   $ 0.40   $ 0.92   $ 1.05  
  — from discontinued operations   $ 0.02       $ 0.01   $ 0.14  
   
 
 
 
 
    $ 0.44   $ 0.40   $ 0.93   $ 1.19  
   
 
 
 
 

Supplemental earnings information:

 

 

 

 

 

 

 

 

 

 

 

 

 
Earnings attributable to common shares, as above     283     254     596     749  
Adjustments:                          
  Earnings from discontinued operations     (9 )   (5 )   (9 )   (92 )
  One time items:                          
    Net losses (gains) on disposals of businesses and investments     28     (3 )   34     (302 )
    Restructuring charges         10     6     30  
    Tax on above items     4     (3 )       66  
    BGM goodwill impairment     67         67      
  Effect of new accounting standard(2)         49         194  
   
 
 
 
 
Adjusted earnings from continuing operations     373     302     694     645  
   
 
 
 
 
Adjusted basic and fully diluted earnings per common share from continuing operations   $ 0.57   $ 0.48   $ 1.08   $ 1.03  
   
 
 
 
 

Notes to consolidated statement of earnings

(1)
Where necessary, certain amounts for 2001 have been reclassified to conform to the current year's presentation. Specifically, the subtotals for "Earnings before interest, tax, depreciation, amortization and restructuring charges" and "Operating profit before amortization and restructuring charges" no longer appear on the face of the consolidated statement of earnings and retained earnings, and "Dividends declared on preference shares" are no longer included in "Earnings from continuing operations." These changes had no effect on "Earnings attributable to common shares" nor on "Earnings per common share."

(2)
Represents the reduction of amortization, net of tax, of identifiable intangible assets and goodwill as if the new accounting standard was in effect in 2001.

Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 7


CONSOLIDATED BALANCE SHEET
(millions of US dollars)

 
  December 31
 
 
  2002
  2001
 
Assets          
Cash and cash equivalents   709   532  
Accounts receivable, net of allowances   1,534   1,700  
Inventories   287   256  
Prepaid expenses and other current assets   274   275  
Deferred income taxes   215   248  
   
 
 
Current assets   3,019   3,011  
Property and equipment, net   1,548   1,552  
Identifiable intangible assets, net   4,713   4,921  
Goodwill   8,076   7,903  
Other non-current assets   1,186   1,263  
   
 
 
Total assets   18,542   18,650  
   
 
 
Liabilities and shareholders' equity          
Liabilities          
Short-term indebtedness   316   620  
Accounts payable and accruals   1,641   1,888  
Deferred revenue   927   882  
Current portion of long-term debt   318   473  
   
 
 
Current liabilities   3,202   3,863  
Long-term debt   3,487   3,651  
Other non-current liabilities   1,131   1,229  
Deferred income taxes   1,768   1,687  
   
 
 
Total liabilities   9,588   10,430  
Shareholders' equity          
Share capital   2,803   2,198  
Cumulative translation adjustment   (64 ) (231 )
Retained earnings   6,215   6,253  
   
 
 
Total shareholders' equity   8,954   8,220  
   
 
 
Total liabilities and shareholders' equity   18,542   18,650  
   
 
 

Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 8


CONSOLIDATED STATEMENT OF CASH FLOW
(millions of US dollars)

 
  Three Months Ended December 31
  Twelve Months Ended December 31
 
 
  2002
  2001
  2002
  2001
 
 
  (unaudited)

   
   
 
Cash provided by (used in):                  
Operating activities                  
Earnings from continuing operations   279   256   606   684  
Add back (deduct) items not involving cash:                  
  Amortization of development costs and capitalized software   10   41   46   104  
  Depreciation   146   119   542   476  
  Amortization   72   127   288   444  
  Net losses (gains) on disposals of businesses and investments   28   (3 ) 34   (302 )
  Deferred income taxes   49   (16 ) 101   75  
  Equity in net losses of associates, net of tax   72   14   101   50  
  Other, net   13   10   46   34  
Voluntary pension contribution   (35 )   (142 )  
Changes in working capital and other items   211   268   69   79  
Cash provided by operating activities — discontinued operations     1     7  
   
 
 
 
 
Net cash provided by operating activities   845   817   1,691   1,651  
Investing activities                  
Acquisitions of businesses and investments   (50 ) (6 ) (272 ) (2,419 )
Proceeds from disposals of businesses and investments   28   45   51   209  
Additions to property and equipment   (167 ) (209 ) (523 ) (684 )
Other investing activities   (33 ) (78 ) (166 ) (359 )
Proceeds from disposal of newspaper businesses     23     239  
Cash used in investing activities — discontinued operations     (1 )   (1 )
   
 
 
 
 
Net cash used in investing activities   (222 ) (226 ) (910 ) (3,015 )

Financing activities

 

 

 

 

 

 

 

 

 
Proceeds from debt     703   400   2,054  
Repayments of debt   (28 ) (55 ) (540 ) (281 )
Net (repayments) borrowings of short-term loan facilities   (281 ) (1,162 ) (604 ) 116  
Proceeds from issuance of common shares       437    
Dividends paid on preference shares   (5 ) (8 ) (22 ) (28 )
Dividends paid on common shares   (75 ) (70 ) (283 ) (279 )
Other financing activities, net     (13 ) (2 ) (19 )
   
 
 
 
 
Net cash (used in) provided by financing activities   (389 ) (605 ) (614 ) 1,563  
   
 
 
 
 
    234   (14 ) 167   199  
Translation adjustments   4   (2 ) 10   (4 )
   
 
 
 
 
Increase (decrease) in cash and cash equivalents   238   (16 ) 177   195  
Cash and cash equivalents at beginning of period   471   548   532   337  
   
 
 
 
 
Cash and cash equivalents at end of period   709   532   709   532  
   
 
 
 
 
Supplemental cash flow information:                  
Net cash provided by operating activities, as above   845   817   1,691   1,651  
Additions to property and equipment, as above   (167 ) (209 ) (523 ) (684 )
Other investing activities, net, as above   (33 ) (78 ) (166 ) (359 )
Dividends paid on preference shares, as above   (5 ) (8 ) (22 ) (28 )
   
 
 
 
 
Free Cash Flow   640   522   980   580  
   
 
 
 
 

Thomson Reports Full-Year/Fourth-Quarter 2002 Results
February 26, 2003
Page 9


BUSINESS SEGMENT INFORMATION*
(millions of US dollars)
(
unaudited)

 
  Three Months Ended December 31
  Twelve Months Ended December 31
 
  2002
  2001
  change
  2002
  2001
  change
Revenues:                        
  Legal and Regulatory   834   838     2,961   2,844   4%
  Learning   677   622   9%   2,290   1,851   24%
  Financial   380   392   -3%   1,543   1,585   -3%
  Scientific and Healthcare   252   218   16%   780   692   13%
  Corporate and other(1)   57   60   -5%   201   222   -9%
  Intercompany eliminations   (13 ) (7 )     (39 ) (32 )  
   
 
     
 
   
  Total ongoing businesses   2,187   2,123   3%   7,736   7,162   8%
  Disposals(2)   3   5       20   75    
   
 
     
 
   
  Total revenues   2,190   2,128   3%   7,756   7,237   7%
   
 
     
 
   
EBITDA:(3)                        
  Legal and Regulatory   331   312   6%   928   860   8%
  Learning   214   165   30%   520   406   28%
  Financial   120   113   6%   418   401   4%
  Scientific and Healthcare   97   79   23%   206   174   18%
  Corporate and other(1)   10   (35 )     (10 ) (52 )  
   
 
     
 
   
  Total ongoing businesses   772   634   22%   2,062   1,789   15%
  Disposals(2)     (5 )     (2 ) (3 )  
   
 
     
 
   
  Total EBITDA   772   629   23%   2,060   1,786   15%
   
 
     
 
   
Adjusted Operating Profit:(3)                        
  Legal and Regulatory   289   274   5%   769   713   8%
  Learning   165   133   24%   354   264   34%
  Financial   77   75   3%   249   252   -1%
  Scientific and Healthcare   90   72   25%   179   150   19%
  Corporate and other(1)   4   (36 )     (29 ) (60 )  
   
 
     
 
   
  Total ongoing businesses   625   518   21%   1,522   1,319   15%
  Disposals(2)   1   (8 )     (4 ) (9 )  
   
 
     
 
   
  Total adjusted operating profit   626   510   23%   1,518   1,310   16%
   
 
     
 
   

Reconciliation of operating profit to adjusted operating profit and EBITDA:(3)

 

 

 

 

 

 

 

 

 

 

 

 
  Operating profit   554   373       1,224   836    
    Add back:                        
      Restructuring charges     10       6   30    
      Amortization   72   127       288   444    
   
 
     
 
   
      Adjusted operating profit   626   510       1,518   1,310    
    Add back:                        
      Depreciation   146   119       542   476    
   
 
     
 
   
      EBITDA   772   629       2,060   1,786    
   
 
     
 
   

        *Notes to business segment information for continuing operations

(1)
Corporate and other includes the results of the Thomson Media group, a non-reportable segment comprised of businesses that provide specialized information to commercial banks and financial services and financial planning companies, as well as corporate costs and costs associated with Thomson stock appreciation rights.

(2)
Disposals consist of the results of businesses sold or held for sale, which do not qualify as discontinued operations.

(3)
The table provides a reconciliation of operating profit within the consolidated statement of earnings to both earnings before interest, tax, depreciation, amortization and restructuring costs (EBITDA) and operating profit before amortization and restructuring costs (adjusted operating profit) included within the business segment information for the three months and the twelve months ended December 31, 2002 and 2001.



QuickLinks

CONSOLIDATED STATEMENT OF EARNINGS (1) (millions of US dollars, except per common share data)
CONSOLIDATED BALANCE SHEET (millions of US dollars)
CONSOLIDATED STATEMENT OF CASH FLOW (millions of US dollars)
BUSINESS SEGMENT INFORMATION* (millions of US dollars) ( unaudited )