Business Description

1 Ark /WM Outrigger 2 HG Global 11 Kudu 17 Distinguished 18 Other Operation s 19 Investments 22 Regulation 23 Ratings 28 Human Capital 28 ITEM 1A. Risk Factors 29 ITEM 1B. Unresolved Staff Comments 42 ITEM 1C. Cybersecurity 42 ITEM 2. Properties 42 ITEM 3. Legal Proceedings 43 ITEM 4. Mine Safety Disclosures 43 Available Information 43 Information About Our Executive Officers 43 PART II ITEM 5. Market for the Company’s Common Equity, Related Shareholder Matters and Issuer Purchases of Equity Securities 44 ITEM 6. Reserved 44 ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations 45 Results of Operations 45 Liquidity and Capital Resources 80 Transactions with Related Persons 85 Non-GAAP Financial Measures 85 Critical Accounting Estimates 87 Forward-Looking Statements 101 ITEM 7A. Quantitative and Qualitative Disclosures About Market Risk 102 ITEM 8. Financial Statements and Supplementary Data 103 ITEM 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure 103 ITEM 9A. Controls and Procedures 104 ITEM 9B. Other Information 104 ITEM 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections 104 PART III ITEM 10. Directors, Executive Officers and Corporate Governance 104 ITEM 11. Executive Compensation 104 ITEM 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters 104 ITEM 13. Certain Relationships and Related Transactions, and Director Independence 105 ITEM 14. Principal Accountant Fees and Services 105 PART IV ITEM 15. Exhibits and Financial Statement Schedules 105 ITEM 16. Form 10-K Summary 107 CERTIFICATIONS C-1 PART I Item 1. Business GENERAL White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”) is an exempted Bermuda limited liability company whose principal businesses are conducted through its subsidiaries and affiliates. Within this report, the term “White Mountains” is used to refer to one or more entities within the consolidated organization, as the context requires. The Company’s headquarters is located at 26 Reid Street, Hamilton, Bermuda HM 11, its principal executive office is located at 23 South Main Street, Suite 3B, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. The Company’s website is located at www.whitemountains.com . The information contained on White Mountains’s website is not incorporated by reference into, and is not a part of, this report. White Mountains is engaged in the business of making opportunistic and value-oriented acquisitions of businesses and assets in the insurance, financial services and related sectors, operating these businesses and assets through its subsidiaries and, if and when attractive exit valuations become available, disposing of these businesses and assets. As of December 31, 2025, White Mountains conducted its business primarily in five areas: property and casualty insurance and reinsurance, municipal bond guarantee reinsurance, capital solutions for asset and wealth management firms, specialty insurance distribution and other operations. White Mountains’s property and casualty insurance and reinsurance business is conducted through its subsidiary Ark Insurance Holdings Limited and its subsidiaries (collectively, “Ark”) and Outrigger Re Ltd. Segregated Account 2023-1 (“WM Outrigger Re”) (collectively with Ark, “Ark/WM Outrigger”). White Mountains’s municipal bond guarantee reinsurance business is conducted through its subsidiary HG Global Ltd. and its reinsurance subsidiary HG Re Ltd. (“HG Re”) (collectively with HG Re, “HG Global”). White Mountains provides capital solutions for asset and wealth management firms through its subsidiary Kudu Investment Management, LLC and its subsidiaries (collectively, “Kudu”). White Mountains’s specialty insurance distribution business is conducted through its subsidiary WM Phoenix Parent, L.P. and its subsidiaries d/b/a Distinguished Programs (collectively, “Distinguished”).…