NYSE: WTM

As of December 31, 2025, White Mountains’s reportable segments were Ark/WM Outrigger, HG Global, Kudu and Distinguished, with its remaining operating businesses, holding companies and other assets included in Other Operations. On December 5, 2025, White Mountains completed the sale of a controlling financial interest in Bamboo. As a result, White Mountains deconsolidated Bamboo on December 5, 2025, and Bamboo is no longer a reportable segment. Through December 5, 2025, Bamboo’s results of operations are presented within the Bamboo segment.

1

ARK/WM OUTRIGGER

Overview

The Ark/WM Outrigger segment consists of Ark and WM Outrigger Re.

On January 1, 2021, White Mountains acquired a controlling ownership interest in Ark (the “Ark Transaction”). Ark is a specialty property and casualty insurance and reinsurance company that offers a wide range of niche insurance and reinsurance products, including property, specialty, marine & energy, casualty and accident & health.

During the fourth quarter of 2022, Ark sponsored the formation of Outrigger Re Ltd., a Bermuda company registered as a special purpose insurer and segregated accounts company, to provide collateralized reinsurance protection on Ark’s Bermuda global property catastrophe excess of loss portfolio written in the 2023 underwriting year. Ark renewed its quota share reinsurance agreement with Outrigger Re Ltd. for the 2024, 2025 and 2026 underwriting years. White Mountains consolidates its segregated account of Outrigger Re Ltd., WM Outrigger Re, in its financial statements. White Mountains’s capital commitment to WM Outrigger Re was $150 million for the 2025 underwriting year, $130 million for the 2024 underwriting year and $205 million for the 2023 underwriting year. WM Outrigger Re is not participating in the 2026 underwriting year; however, WM Outrigger Re remains exposed to losses that occur prior to the expiration of the 2025 underwriting year on June 30, 2026.

Ark

Ark is a specialty property and casualty insurance and reinsurance company that offers a wide range of niche insurance and reinsurance products. Ark underwrites select coverages through its two major subsidiaries in the United Kingdom and Bermuda.

In the United Kingdom, Ark participates in the Lloyd’s of London (“Lloyd’s”) market through Ark Corporate Member Limited (“ACML”), Ark’s wholly-owned Lloyd’s corporate member, which in turn provides underwriting capacity to Lloyd’s Syndicates 4020 and 3902 and Additional Central Settlement Number (“ACSN”) 3832 (collectively, the “Syndicates”). ACSN 3832 writes business on behalf of Syndicate 4020. Ark Syndicate Management Limited (“ASML”), Ark’s wholly-owned Lloyd’s managing agent, oversees the underwriting of the Syndicates. The Syndicates underwrite a diversified portfolio of insurance and reinsurance product lines, including property, specialty, marine & energy, casualty and accident & health. Syndicate 4020 commenced underwriting on April 1, 2007, Syndicate 3902 on January 1, 2017 and ACSN 3832 on July 1, 2024.

In Bermuda, Ark underwrites through its wholly-owned subsidiary, Group Ark Insurance Limited (“GAIL”), a Class 4 Bermuda-domiciled insurance and reinsurance company. GAIL underwrites a diversified portfolio of insurance and reinsurance product lines, including property, marine & energy, specialty, casualty and accident & health lines. GAIL commenced underwriting third-party business in January 2021. In addition, GAIL provides capital to support ACML’s capital requirements at Lloyd’s (“Funds at Lloyd’s”). In November 2025, AM Best affirmed GAIL’s financial strength rating at “A/stable.”

In both jurisdictions, Ark underwrites business primarily through insurance and reinsurance brokers and wholesalers, both in the open market and through managing general agents (“MGAs”).

As of December 31, 2025 and 2024, White Mountains reported $6,146 million and $5,134 million of total assets and $1,594 million and $1,438 million of total equity related to Ark. As of December 31, 2025 and 2024, White Mountains owned 72.1% of Ark on a basic shares outstanding basis (61.9% after taking account of management’s equity incentives) and reported $465 million and $410 million of noncontrolling interests related to Ark. The remaining shares are owned by current and former employees of Ark. In the future, management rollover shareholders could earn additional shares in Ark if and to the extent that White Mountains achieves certain thresholds for its multiple of invested capital return. If fully earned, these shares would represent an additional 12.3% of the shares outstanding as of December 31, 2025.

2

WM Outrigger Re

During the fourth quarter of 2022, Ark sponsored the formation of Outrigger Re Ltd., a Bermuda company registered as a special purpose insurer and segregated accounts company, to provide reinsurance capacity to Ark. Outrigger Re Ltd. was initially capitalized with $250 million of preference shares for business written in the 2023 underwriting year, of which White Mountains contributed $205 million. The remaining capital was provided by third-party investors. Outrigger Re Ltd. entered into collateralized quota share agreements with GAIL to provide reinsurance protection on Ark’s Bermuda global property catastrophe excess of loss portfolio written in the 2023 underwriting year. The proceeds from the issuance of the preference shares were deposited into collateral trust accounts to fund any potential obligations under the reinsurance agreements with GAIL. Outrigger Re Ltd.’s obligations under the reinsurance agreements with GAIL are subject to an aggregate limit equal to the assets in the collateral trusts at any point in time. The terms of the reinsurance agreements are renewable upon the mutual agreement of Ark and the applicable preference shareholder of Outrigger Re Ltd.

During the fourth quarter of 2023, Ark renewed Outrigger Re Ltd. for the 2024 underwriting year with $250 million of capital. White Mountains rolled over $130 million from its commitment to the 2023 underwriting year. The remaining capital was provided by third-party investors.

During the fourth quarter of 2024, Ark renewed Outrigger Re Ltd. for the 2025 underwriting year with $230 million of capital. White Mountains’s total commitment was $150 million, of which $130 million was rolled over from its commitment to the 2024 underwriting year. The remaining capital was provided by third-party investors. The reduced capacity at Outrigger Re Ltd. was replaced by Ark through traditional quota share reinsurance agreements. During the year ended December 31, 2024, White Mountains received net distributions of $123 million from WM Outrigger Re, which included a net return of capital related to changes in White Mountains’s capital commitments for the 2024 and 2025 underwriting years and reinsurance profits for the 2023 underwriting year. During the year ended December 31, 2024, WM Outrigger Re commuted its reinsurance agreement with GAIL for the 2023 underwriting year.

During the fourth quarter of 2025, Ark renewed Outrigger Re Ltd. for the 2026 underwriting year with $70 million of capital. The reduced capacity at Outrigger Re Ltd. was replaced by Ark through traditional quota share reinsurance agreements. The capital was provided entirely by third-party investors excluding White Mountains. During the year ended December 31, 2025, White Mountains received net distributions of $10 million from WM Outrigger Re, related primarily to reinsurance profits for the 2024 underwriting year. In January 2026, White Mountains received a distribution of $128 million, which included a net return of capital related to its non-renewal for the 2026 underwriting year. White Mountains expects to receive additional distributions of reinsurance profits from the 2025 underwriting year in 2026.

As of December 31, 2025 and 2024, White Mountains reported $270 million and $236 million of total assets and $232 million and $196 million of total equity related to WM Outrigger Re. As of December 31, 2025 and 2024, White Mountains owned 100% of WM Outrigger Re’s preferred equity.

Insurance and Reinsurance Overview

Generally, insurance companies underwrite insurance policies in exchange for premiums paid by their customers (the insureds). An insurance policy is a contract between the insurance company and the insured where the insurance company agrees to pay for losses suffered by the insured or a third-party claimant that are covered under the contract. Such contracts are often subject to subsequent legal interpretation by courts, legislative action and arbitration.

Reinsurance is an arrangement in which a reinsurance company (the reinsurer) agrees to indemnify an insurance company (the ceding company) for insurance risks underwritten by the ceding company. Reinsurance can benefit a ceding company in several ways, including reducing net exposure to individual risks, providing protection from large or catastrophic losses and assisting in maintaining required capital levels and financial or operating leverage ratios. Reinsurance can provide a ceding company with additional underwriting capacity by permitting it to accept larger risks and underwrite a greater number of risks without increasing its capital as much as would be the case without reinsurance. Reinsurers may also purchase reinsurance for themselves, which is known as retrocessional reinsurance, to cover risks assumed from ceding companies. Reinsurance companies often enter into retrocessional reinsurance agreements for many of the reasons that ceding companies enter into reinsurance agreements.

Reinsurance is generally written on a treaty or facultative basis. Treaty reinsurance is an agreement whereby the reinsurer assumes a specified portion or category of risk under all qualifying policies issued by the ceding company during the term of the agreement, usually one year. When underwriting treaty reinsurance business, the reinsurer does not evaluate each individual risk and generally accepts the original underwriting decisions made by the ceding company. Treaty reinsurance is typically written on either a proportional or excess of loss basis. A proportional reinsurance treaty is an arrangement whereby a reinsurer assumes a predetermined proportional share of the premiums and losses generated on specified business. An excess of loss reinsurance treaty is an arrangement whereby a reinsurer assumes losses that exceed a specific retention of loss by the ceding company. Facultative reinsurance, on the other hand, is underwritten on a risk-by-risk basis, which allows the reinsurer to determine individual pricing for each exposure.

3

Insurance and reinsurance companies incur a significant amount of their total expenses from policy obligations, which are commonly referred to as claims or losses. In settling claims, various loss adjustment expenses (“LAE”) are incurred such as insurance adjusters’ fees and litigation expenses. Loss and LAE are categorized by the year in which the policy is underwritten (the year of account or underwriting year) for purposes of Ark’s claims management and estimation of the ultimate loss and LAE reserves. For purposes of Ark’s reporting under GAAP, loss and LAE are categorized by the year in which the claim is incurred (the accident year). In the following calendar years, as Ark increases or decreases its estimate for the ultimate loss and LAE for claims in prior underwriting years, or prior accident years for reporting under GAAP, it will record favorable or unfavorable loss reserve development, which is recorded in the calendar year when such loss reserve development is determined. In addition, insurance companies incur policy acquisition expenses, such as commissions paid to agents and premium taxes, and other expenses related to the underwriting process, including employee compensation and benefits. A key measure of absolute and relative underwriting performance for an insurance company is the combined ratio. An insurance company’s combined ratio is calculated by adding the ratio of incurred loss and LAE to earned premiums (the loss ratio) and the ratio of policy acquisition and other underwriting expenses to earned premiums (the expense ratio). A combined ratio under 100% indicates that an insurance company is generating an underwriting profit, while a combined ratio over 100% indicates that an insurance company is generating an underwriting loss.

Ark derives substantially all of its revenues from earned premiums, investment income and net realized and unrealized investment gains (losses). Ark also receives fee revenues and profit commissions from business ceded to its reinsurers across multiple classes of business. Written premiums represent the amount charged to an insured or reinsured party to provide coverage under an insurance or reinsurance contract, which are recognized as earned premiums within revenue over the period that insurance coverage period is provided (i.e., ratably over the life of the policy or, in the case of catastrophe premiums, in proportion to the level of insurance protection provided.) Unearned premiums represent the portion of premiums written that are applicable to future insurance coverage provided by policies. A significant period often elapses between receipt of insurance premiums and payment of insurance claims. During this time, Ark invests the premiums, earns investment income and generates net realized and unrealized investment gains (losses).

Lines of Business

Ark writes specialized lines of insurance and reinsurance across its United Kingdom and Bermuda platforms within five major lines of business: property, specialty, marine & energy, casualty and accident & health. Claims for property, specialty, marine & energy and accident & health coverages are typically reported and settled in a relatively short period of time. Casualty insurance (often referred to as liability insurance) generally covers the financial consequences of a legal liability of an individual or an organization resulting from negligent acts or omissions causing bodily injury, property damages and/or economic damages to a third-party. Settlements for casualty/liability coverages can extend for long periods of time as claims are often reported and ultimately paid or settled years after the related loss events occur.

Ark has recently added new products and lines of business to its portfolio, as it focuses on profitable business opportunities while carefully managing underwriting risk. Ark also leads certain Lloyd’s market consortia, including two that target renewable energy clients including wind farms, solar plants, hydroelectric plants, geothermal plants and wave and tidal projects, as well as others that focus on property and power outage coverages.

The following table presents Ark’s gross written premiums by line of business for the years ended December 31, 2025, 2024 and 2023:

Year Ended December 31,

Millions202520242023

Property$1,178.0 $1,080.8 $917.0

Specialty646.7450.0436.6

Marine & Energy453.6449.6375.7

Casualty168.8130.698.7

Accident & Health110.196.070.4

Total gross written premiums$2,557.2 $2,207.0 $1,898.4

4

A description of Ark’s business written within each line of business follows:

Property

Ark’s property business is underwritten on both an insurance and reinsurance basis covering the financial consequences of accidental losses to an insured’s property, such as a business’s building, inventory and equipment, or personal property. Coverages provided include all risks of direct physical loss or damage, business interruption and natural and non-natural catastrophe perils. Ark’s property insurance business consists primarily of direct and facultative contracts, line slips and MGA binding authorities. Ark’s property insurance business is underwritten on a worldwide basis with a focus on excess & surplus lines in the United States and on large international accounts. Ark’s property reinsurance business consists primarily of treaty reinsurance underwritten on a catastrophe excess of loss, per risk excess and proportional basis. Ark’s property reinsurance business is underwritten on a worldwide basis with particular focus on risks in the United States and Europe. Ark also underwrites structured property business, which provides reinsurance capacity to primary fronting insurance companies, net after inuring reinsurance, with a limited downside risk profile that is managed through aggregated collateralized limits.

Specialty

Ark’s specialty business is underwritten on both an insurance and reinsurance basis covering a range of individual risks and treaties primarily including aviation, contingency, cyber, fine art & specie, mortgage, nuclear, political and credit, space, surety as well as terrorism and political violence. Ark’s specialty insurance and reinsurance business is underwritten on a worldwide basis.

Aviation

Aviation insurance primarily covers airlines and general aviation for loss of, or damage to, aircraft hull and ensuing passenger and third-party liability. Perils include war and war-like actions such as terrorism, hijacking, confiscation, expropriation, nationalization and deprivation. Additionally, liability arising out of non-aircraft operations such as hangars and airports may be covered.

Contingency

Contingency insurance primarily covers cancellation and abandonment of events, non-appearance, prize indemnity and film and television insurance. Ark’s contingency insurance and reinsurance business is underwritten on a worldwide basis.

Cyber

Cyber insurance primarily covers the physical damage and liabilities arising from cyber attacks, including coverage for ransomware, loss of data, incident response costs, business interruption and third-party liabilities.

Fine Art & Specie

Fine art & specie insurance primarily covers loss to fine art, specie, cash in transit and vault and jewelers’ block risks as a result of theft or damage in transit or at exhibition.

Mortgage

Mortgage insurance covers financial guarantee and credit risks between a lending institution and a borrower designed to address responsibility for debt payments and default. Ark underwrites a reinsurance portfolio supporting government-sponsored enterprises (Fannie Mae and Freddie Mac) and private mortgage insurers on both a proportional and excess of loss basis.

Nuclear

Nuclear insurance covers country specific nuclear pools and companies and institutions with nuclear exposure excluded from standard property and casualty policies for coverage of physical damage and third-party liability.

Political and Credit

Political and credit insurance primarily covers risks relating to the confiscation, expropriation, nationalization and deprivation of insured assets due to war, political or government action as well as contract frustration and non-payment by obligors.

Space

Space insurance primarily covers loss of, or damage to, satellites during launch and in orbit, including faulty design that leads to early loss of operating life. Ark’s space insurance is primarily written through binders supporting specialized, technical MGAs.

5

Surety

Surety insurance covers financial guarantee risks between a bond issuer, principal and obligee designed to address responsibility for debt payments, default or other financial obligations. Ark underwrites this portfolio on a reinsurance basis, primarily excess of loss, for U.S.-domiciled clients. The underlying assureds cover a variety of industries including construction, oil & gas, hotel & leisure and transportation projects.

Terrorism and Political Violence

Terrorism and political violence insurance primarily covers physical loss or damage and threat thereof, including ensuing loss through business interruption, caused by declared terror events, political violence and war and war-like actions in developed and developing countries around the world.

Marine & Energy

Ark’s marine & energy business is underwritten on both an insurance and reinsurance basis primarily covering marine hull, cargo, specie, marine & energy liabilities and upstream energy platform physical damage and liability. Marine hull consists primarily of coastal and ocean-going vessels and covers worldwide risks on an all perils or total loss only basis together with lighter craft, including yachts. Cargo consists of worldwide transits and moveable goods with a particular emphasis on bulk cargo, project cargo and pre-launch satellite risks. Specie is the transit and storage of high value goods including semi-precious and precious metals. Marine & energy liabilities consist of liability risks arising from doing business in their respective industries including liabilities arising from pollution and damage covered by protection and indemnity clubs, including for example the International Group of Protection & Indemnity Clubs. Upstream energy platform physical damage and liability covers a variety of oil and gas industry construction, exploration and production risks.

Ark’s marine & energy insurance business consists of direct and facultative risks written primarily in the open market, as well as through line slips and MGA binding authorities. Ark’s marine & energy reinsurance business consists of treaty reinsurance underwritten on both a proportional and excess of loss basis. Ark’s marine & energy insurance and reinsurance business is underwritten on a worldwide basis.

Casualty

Ark’s casualty business is underwritten on an insurance and reinsurance basis primarily covering medical malpractice, professional liability and general liability. Ark’s casualty insurance business is generally written on an excess of loss and primary basis for a wide range of U.S. and non-U.S. companies, including (i) public entities, (ii) energy, transportation, chemical, manufacturing and construction companies and (iii) legal, accounting, consulting, architectural and engineering firms. Ark’s casualty reinsurance business is underwritten on an excess of loss and proportional treaty basis.

Accident & Health

Ark’s accident & health business is underwritten on both an insurance and reinsurance basis covering a wide range of personal accident, sickness, disability, travel, short-term life, health and medical insurance and reinsurance risks. Ark’s accident & health insurance and reinsurance business consists of direct and facultative contracts written under the binding authority of external MGAs and through Accident & Health Underwriting Limited (“AHU”), Ark’s wholly-owned MGA domiciled in the United Kingdom. Ark’s accident & health insurance and reinsurance business is underwritten on a worldwide basis.

Geographic Concentration

The following table shows Ark’s gross written premiums by geographic region based on the location of Ark’s underwriting offices for the years ended December 31, 2025, 2024 and 2023:

MillionsYear Ended December 31,

Gross written premiums by country202520242023

United Kingdom$1,404.7 $1,229.5 $1,027.8

Bermuda1,152.5 977.5 870.6

Total$2,557.2 $2,207.0 $1,898.4

6

Marketing and Distribution

Ark offers its products and services through a network of brokers, MGAs and reinsurance intermediaries (collectively, “insurance and reinsurance intermediaries”). In the United Kingdom, Ark operates through the Syndicates with Lloyd’s approved brokers and MGAs. In Bermuda, Ark primarily derives its reinsurance business through insurance and reinsurance intermediaries that represent the ceding company and its insurance business through brokers based in Bermuda and London. Ark pays commissions to brokers, MGAs and reinsurance intermediaries as compensation for facilitating the flow and processing of business, typically on industry standard percentages of premium underwritten. In addition, Ark pays certain MGAs profit commissions based on the underwriting profit of the business they produce.

During the years ended December 31, 2025, 2024 and 2023, Ark received a significant portion of its gross written premiums from five insurance and reinsurance intermediaries. The following table shows the proportion of business produced by the top five insurance and reinsurance intermediaries for the years ended December 31, 2025, 2024 and 2023:

Year Ended December 31,

Gross written premiums by insurance and reinsurance intermediary202520242023

Marsh & McLennan Companies, Inc.24.3 %25.8 %27.5 %

Arthur J. Gallagher & Co15.2 12.5 16.9

Aon plc12.4 13.4 16.7

Howden Insurance Group
8.7 6.4 4.6

Willis Towers Watson plc4.1 4.9 5.0

Total proportion of business produced by the top five

insurance and reinsurance intermediaries
64.7 %63.0 %70.7 %

Underwriting and Pricing

Ark aims to build a diversified and balanced portfolio of risks that generates an underwriting profit each year. Ark believes in a disciplined underwriting strategy that aims to consistently outperform the market. In hard market conditions, Ark aims to grow premiums, as pricing, terms and conditions and limit deployment are more favorable and can lead to enhanced returns on capital. In soft markets, Ark is willing to reduce its business volume when pricing, terms and conditions and limit deployment can make it more difficult to achieve an adequate return on capital. Ark is willing to forgo business if it believes it is not priced appropriately for the exposure or risk assumed.

Ark operates an underwriting controls framework which includes individual underwriting authorities, continuous quality monitoring and peer review of risks. The framework aims to ensure a high quality of underwriting through monitoring of pricing and rate change, contract certainty and appropriate terms and conditions. The nature of delegated underwriting naturally increases the risk of underwriting, through the ability of third parties being able to bind Ark to risks without detailed review of the risk involved. This risk is mitigated through the application of strict underwriting guidelines, managed by a dedicated team within the Ark compliance department. This team reviews MGA and third-party binding authority approvals pre-bind and monitors a program of audits to ensure compliance with regulations and guidelines.

Ark uses bespoke pricing models for each of the products that it underwrites. These pricing models seek to generate a pricing metric required to achieve an acceptable return on capital for each class of business, and each of the risks priced therein. These models rely on several factors depending on the class of business, including exposure analysis, historical experience, estimates of future loss costs, claims experience and natural catastrophe outlook, including the physical risk of climate change and inflation. See “Ark — Catastrophe Risk Management and Reinsurance Protection” on page 8.

Ark actively monitors price adequacy at various points between individual risks and the portfolio level to measure and evaluate overall performance. In addition, Ark updates rates to achieve targeted returns on capital at an individual risk as well as portfolio level to enhance return on capital.

7

Competition

Specialized lines of insurance and reinsurance are highly competitive. Ark competes with other Lloyd’s syndicates, London market participants and major U.S., Bermuda, European and other international insurance and reinsurance companies. The significant competitive factors for most products are price, terms and conditions, broker relationships, underwriting service, financial strength rating and claims service. Ark competes with insurance and reinsurance companies who operate in the Bermuda and Lloyd’s markets such as:

•Bermuda insurance and reinsurance market: American International Group, Inc., Arch Capital Group Ltd., Ascot Group Ltd., Aspen Insurance Holdings Ltd., Chubb Ltd., Everest Re Group, Markel Group, Inc., RenaissanceRe Holdings Ltd., Sompo Holdings Inc., SiriusPoint Ltd. and others;

•Lloyd’s market: AXIS Capital Holdings Ltd., Beazley plc, Canopius Group Ltd., Convex Group Ltd., Hiscox plc, Lancashire Holdings Ltd., QBE Insurance Group Ltd. and other syndicates.

Claims Management

Effective claims management is a critical factor in achieving satisfactory underwriting results. Ark maintains an experienced staff of dedicated claims handlers and loss adjusters. These individuals seek to ensure that Ark has the appropriate level of expertise to handle complex claims. Within the claims departments, Ark also uses various shared services. These include third-party claims administrators, particularly for lower value, less specialized claims (for example in Ark’s MGA-produced business), subrogation and recovery support and legal representation.

For business written in the Lloyd’s market, claims handling and case reserves are established in accordance with the applicable Lloyd’s Claim Scheme and Lloyd’s Claims Management Principles and Oversight Framework.

Catastrophe Risk Management and Reinsurance Protection

Catastrophe Risk Management

Ark

Ark has exposure to losses caused by unpredictable catastrophic events all over the world including natural and other disasters such as hurricanes, windstorms, earthquakes, floods, wildfires, tornadoes, tsunamis and severe weather. Catastrophes can also include large losses driven by public health crises, terrorist attacks, war and war-like actions, explosions, infrastructure failures and cyber attacks. The extent of a catastrophe loss is a function of both the severity of the event and total amount of insured exposure to the event, as well as the coverage provided to customers. Increases in the value and concentration of insured property or insured employees, the effects of inflation, changes in weather patterns and increased terrorism and war and war-like actions could increase the future frequency and/or severity of claims from catastrophic events. Climate change, which is characterized by higher temperatures, sea level rise and more extreme weather events including droughts, heavy storms, wildfires and stronger hurricanes, increases the frequency and severity of certain major natural catastrophes. There is also a growing threat of cyber catastrophes due to the increasing interconnectivity of global systems and artificial intelligence.

Ark seeks to manage its exposure to catastrophic losses by limiting and monitoring the aggregate insured value of policies in geographic areas with exposure to catastrophic events and by buying reinsurance. To manage, monitor and analyze insured values and potential losses, Ark utilizes proprietary and third-party catastrophe management software to estimate potential losses for many different catastrophe scenarios. Ark incorporates the physical risk of climate change in its underwriting process through sensitivity and stress testing of its catastrophe models, including increased frequency of U.S. windstorms and the implications of storm surge.

8

Ark licenses third-party global property catastrophe models from Risk Management Solutions Inc. and Karen Clark & Company, as well as utilizes its own proprietary models to calculate expected probable maximum loss (“PML”) estimates from various property and non-property catastrophe scenarios. Ark prices property catastrophe contracts using its own proprietary models, utilizing inputs from third-party software and other data as appropriate. For business that Ark determines to have exposure to catastrophic perils, as part of its underwriting process, it models and evaluates the exposure to assess whether there is an appropriate premium charged for the exposure assumed.

Ark’s two largest natural catastrophe PML zones on a per occurrence basis for a 1-in-250 year event, as measured on a net after-tax exposure basis, are U.S. windstorm and U.S. earthquake. The net after-tax exposure is net of amounts ceded to reinsurers and reinstatement premiums. Different perils are more prevalent at different times of the year, and Ark tailors its outwards reinsurance program to incept accordingly. Once the placement of Ark’s 2026 outwards reinsurance program is completed, Ark expects its net after-tax peak exposure for a 1-in-250 year event related to its largest PML zone to approximate 20-35% of its tangible capital (tangible book value plus debt). Ark’s tangible capital was $1,833 million as of December 31, 2025.

In addition, Ark also has loss exposures to other global natural catastrophe events including, but not limited to, Japanese earthquakes, Japanese windstorms, European windstorms and U.S. wildfires.

Ark’s estimates of potential losses are dependent on many variables, including assumptions about storm intensity, storm surge and loss amplification, loss adjustment expenses and insurance-to-value in the aftermath of weather-related catastrophes. In addition, Ark has to account for quality of data provided by insureds. Accordingly, if the assumptions are incorrect, the losses Ark might incur from an actual catastrophe could be materially different than the expectation of losses generated from modeled catastrophe scenarios. There could also be unmodelled losses which exceed the amounts estimated for U.S. windstorm and U.S. earthquake catastrophes.

Outside of natural catastrophe losses, Ark has exposure to non-natural or man-made large losses. The current largest exposures are cyber, offshore energy production platforms, aviation, terrorism events, war and war-like actions and political risk. Ark uses data from clients and combines this with accumulation tools and PML assessments to obtain potential loss scenarios.

Cyber losses can be derived from a number of scenarios that include major data security breach on large multinational organizations, business blackout from cyber attack on power generation and distribution facilities, malicious attack on cloud service provider data center and ransomware contagion across both individual and multiple corporations. Catastrophic losses in respect of offshore energy production platforms can include physical damage, business interruption, pollution liability, extra expenses and control of oil or gas flow therefrom. Aviation can include physical damage, passenger and third-party liability, hijacking, confiscation, expropriation, nationalization and deprivation. Terrorism and war and war-like actions can include physical damage, business interruption, liability, loss of life and fire following at locations around the world either in a single city or in coordinated attacks across multiple cities, countries or regions. Political and credit risk scenarios can include confiscation, expropriation, nationalization and deprivation of assets, non-payment of financial obligations and mortgage default. Ark estimates its largest net after-tax loss from non-natural/man-made loss scenarios to be less than 10% of its tangible capital.

9

WM Outrigger Re

WM Outrigger Re has exposure to losses caused by unpredictable catastrophic events including natural and other disasters all over the world such as hurricanes, windstorms, earthquakes, floods, wildfires, tornadoes, tsunamis, severe weather and related infrastructure failures. The extent of a catastrophe loss is a function of both the severity of the event and total amount of insured exposure to the event, as well as the coverage provided to customers. Increases in the value and concentration of insured property, the effects of inflation and changes in weather patterns could increase the future frequency and/or severity of claims from catastrophic events. Climate change, which is characterized by higher temperatures, sea level rise and more extreme weather events including droughts, heavy storms, wildfires and stronger hurricanes, increases the frequency and severity of certain major natural catastrophes.

WM Outrigger Re is not providing reinsurance to GAIL for the 2026 underwriting year. However, WM Outrigger Re remains exposed to natural catastrophe events that occur prior to the expiration of the 2025 underwriting year on June 30, 2026. WM Outrigger Re’s two largest remaining natural catastrophe PML zones on a per occurrence basis for a 1-in-250 year event as of January 2026, as measured net of reinstatement premiums, are U.S. earthquake and Japanese windstorm. These two loss events would each represent less than 1% of White Mountains’s common equity. WM Outrigger Re’s obligations under its reinsurance agreement with GAIL are subject to an aggregate limit equal to the assets in the collateral trust at any point in time.

Reinsurance Protection

As part of its enterprise risk management function, Ark purchases reinsurance for risk mitigation purposes. Ark utilizes reinsurance and retrocession agreements to reduce earnings volatility, protect capital, limit its exposure to risk concentration and accumulation of loss and manage within its overall internal risk tolerances or those set and agreed by regulators, ratings agencies and Lloyd’s. Ark also enters into reinsurance and retrocession agreements to reduce its liability on individual risks and enable it to underwrite policies with higher limits where Ark believes this has a broader business benefit.

Ark seeks to protect its downside risk from catastrophes and large loss events by purchasing reinsurance, including quota share and excess of loss protections, aggregate covers and industry loss warranties. Ark also considers alternative structures such as collateralized reinsurance, retrocessional reinsurance and catastrophe bonds.

During the fourth quarter of 2023, 2024 and 2025, Ark renewed its collateralized quota share agreements with Outrigger Re Ltd., a Bermuda special purpose insurer, covering Ark’s Bermuda global property catastrophe excess of loss portfolio written in the 2024, 2025 and 2026 underwriting years, respectively.

The purchase of reinsurance does not discharge Ark from its primary liability for the full value of its policies, and thus the collectability of balances due from Ark’s reinsurers is critical to its financial strength. Ark monitors the financial strength and ratings of its reinsurers on an ongoing basis. See Note 6 — “Third-Party Reinsurance” on page F-47 for a discussion of Ark’s top reinsurers.

Ark’s Loss and LAE Reserves

Ark establishes loss and LAE reserves that are estimates of amounts needed to pay claims and related expenses in the future for insured events that have already occurred, including both reported and unreported claims. Loss reserves are established due to the significant periods of time that may occur between the occurrence, reporting and payment of a loss. The process of estimating reserves involves a considerable degree of judgment by management and is inherently uncertain. See “CRITICAL ACCOUNTING ESTIMATES — Loss and LAE Reserves” on page 90 and Note 5 — “Loss and Loss Adjustment Expense Reserves” on page F-36 for a full discussion regarding Ark’s loss reserving process.

10

HG GLOBAL

Overview

The HG Global segment consists of HG Global and, prior to its deconsolidation on July 1, 2024, the consolidated results of Build America Mutual Assurance Company (“BAM”). See Note 2 — “Significant Transactions” on page F-19.

HG Global was established to fund the startup of BAM and provide reinsurance protection to BAM’s municipal bond insured portfolio. HG Global, together with its subsidiaries, funded the initial capitalization of BAM through the purchase of $503 million of surplus notes issued by BAM (the “BAM Surplus Notes”). HG Global, through its reinsurance subsidiary, HG Re, is a party to a first-loss reinsurance treaty (“FLRT”) with BAM, under which HG Re provides first-loss protection of up to 15%-of-par outstanding for each policy assumed from BAM. HG Re is only licensed to provide reinsurance to BAM. HG Re is required to provide reinsurance on policies that fall within the FLRT underwriting guidelines agreed upon by HG Re.

BAM is the first and only mutual municipal bond insurance company in the United States. By insuring the timely payment of principal and interest on municipal bonds, BAM provides market access to, and lowers interest expense for, issuers of municipal bonds used to finance essential public purpose projects. As a mutual insurance company, BAM is owned by and operated for the benefit of its members, the municipalities whose debt issuances are insured by BAM. BAM is domiciled in New York and is regulated by the New York State Department of Financial Services (“NYDFS”).

White Mountains does not have an ownership interest in BAM. However, through June 30, 2024, White Mountains was required to consolidate BAM’s results in its financial statements because BAM is a variable interest entity (“VIE”) for which White Mountains was the primary beneficiary. BAM’s results were all attributed to noncontrolling interests. On July 1, 2024, HG Re and BAM amended the FLRT with respect to certain governance rights held by HG Re. As a result, and in combination with other governance changes at BAM, White Mountains concluded that it no longer has the power to direct BAM’s activities that most significantly impact its economic performance and is no longer BAM’s primary beneficiary. Accordingly, as of July 1, 2024, White Mountains no longer consolidates BAM. Through June 30, 2024, BAM’s results of operations, are presented within the HG Global segment. See Note 2 — “Significant Transactions” on page F-19.

HG Global has two primary sources of cash flows: (i) interest payments on the BAM Surplus Notes that are made outside the Collateral Trusts and (ii) releases of excess balances from the Collateral Trusts. See “Collateral Trusts” on page 12.

As of December 31, 2025 and 2024, White Mountains reported $1,237 million and $1,179 million of total assets and $210 million and $253 million of total equity related to HG Global. HG Global’s total equity attributable to White Mountains’s common shareholders after intercompany eliminations related to preferred dividends payable to White Mountains and intercompany debt was $756 million and $729 million as of December 31, 2025 and 2024. As of December 31, 2025 and 2024, White Mountains owned 96.9% of HG Global’s preferred equity and 88.4% of its common equity. As of December 31, 2025 and 2024, White Mountains reported $(18) million and $(13) million of noncontrolling interests related to HG Global.

Reinsurance Treaties

HG Global provides reinsurance exclusively to BAM. Through the reinsurance relationship with BAM, HG Global maintains a direct dialogue and line of sight into key operations, including the application of both BAM’s underwriting guidelines and the FLRT underwriting guidelines, continuous portfolio monitoring, credit surveillance and claims paying resources.

HG Global reinsures all BAM policies that meet the FLRT underwriting guidelines. This has resulted in a portfolio with a focus on prudent single risk limits for small-to-medium sized, public investment grade municipal bonds in the United States (primarily in the AA, A and BBB categories in low-risk, stable sectors) that are issued to finance essential public purpose projects, such as schools, utilities and transportation facilities. White Mountains believes that municipal bonds insured by BAM have strong appeal to retail investors, who buy smaller, less liquid issuances, have less portfolio diversification and have fewer credit differentiation skills and analytical resources than institutional investors.

HG Re, through its reinsurance treaties with BAM, is exposed to climate-related events to the extent that those events impact a municipal issuer’s ability to service its debt obligations. Under the FLRT underwriting guidelines, BAM incorporates climate change risk in its credit underwriting process. In doing so, BAM considers both the short-term economic impact from climate change-related severe weather events (including flooding, wildfires, drought, windstorms and tornadoes), as well as longer-term impacts on population and property values from rising sea levels and changing temperature patterns.

11

FLRT

Under the FLRT, HG Re provides first-loss reinsurance protection of up to 15%-of-par outstanding for each policy assumed from BAM. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. HG Re is required to provide reinsurance on policies that fall within the FLRT underwriting guidelines agreed upon by HG Re.

BAM charges an insurance premium on each municipal bond insurance policy it underwrites. Historically, approximately 55% of the total insurance premium charged by BAM has been a member surplus contribution (“MSC”), and the remainder is a risk premium. In return for the reinsurance provided, HG Re receives approximately 60% of the risk premium charged, which is net of a ceding commission.

The FLRT is a perpetual agreement with terms that can be renegotiated every five years. For the next renegotiation period, either party may provide notice during 2028 to trigger a renegotiation that would take effect on January 1, 2030. If the parties are unable to mutually agree to amended terms, the dispute is resolved through arbitration, according to certain principles agreed to by the parties. Amended contract terms must be approved by the NYDFS. Should BAM consider the amended terms unacceptable, it has the option to purchase HG Re or cause another reinsurer to purchase HG Re, at fair value.

In addition, the FLRT provides HG Holdings Ltd., a subsidiary of HG Global, the right to designate two directors for election to BAM’s Board of Directors.

For the year ended December 31, 2025, HG Re recognized gross written premiums of $61 million and earned premiums of $31 million. Prior to the deconsolidation of BAM on July 1, 2024, HG Re’s reinsurance balances under the FLRT eliminated in White Mountains’s consolidated financial statements. For the period from July 1, 2024 to December 31, 2024, HG Re recognized gross written premiums of $32 million and earned premiums of $15 million during the year ended December 31, 2024.

XOLT

HG Re is also party to an excess of loss reinsurance agreement (the “XOLT”) with BAM under which HG Re provides last-dollar protection for exposures on municipal bonds insured by BAM in excess of the NYDFS single issuer limits. As of December 31, 2025, the XOLT is subject to an aggregate limit equal to the lesser of $125 million or the assets held in the supplemental collateral trust (the “Supplemental Trust”) at any point in time. The XOLT is accounted for using deposit accounting, as the agreement does not meet the risk transfer requirements necessary to be accounted for as reinsurance. Accordingly, any financing revenues related to the XOLT are recorded in other revenues,

Prior to the deconsolidation of BAM on July 1, 2024, HG Re’s reinsurance balances under the XOLT eliminated in White Mountains’s consolidated financial statements. For the year ended December 31, 2025 and for the period from July 1, 2024 to December 31, 2024, other revenues recognized by HG Re related to the XOLT were insignificant.

Collateral Trusts

HG Re’s obligations under the FLRT are subject to an aggregate limit equal to the assets in two collateral trusts, the Supplemental Trust and the Regulation 114 Trust (together, the “Collateral Trusts”), at any point in time.

On a monthly basis, BAM deposits cash equal to ceded premiums net of ceding commissions, due to HG Re under the FLRT directly into the Regulation 114 Trust. The Regulation 114 Trust target balance is equal to HG Re’s unearned premiums and unpaid loss and LAE reserves, if any. If, at the end of any quarter, the Regulation 114 Trust balance is below the target balance, funds will be withdrawn from the Supplemental Trust and deposited into the Regulation 114 Trust in an amount equal to the shortfall. If, at the end of any quarter, the Regulation 114 Trust balance is above 102% of the target balance, funds will be withdrawn from the Regulation 114 Trust and deposited into the Supplemental Trust. The Regulation 114 Trust balance as of December 31, 2025 and 2024 was $399 million and $352 million, which consisted of cash, investments and accrued investment income.

The Supplemental Trust target balance is $603 million, less the amount of cash and securities in the Regulation 114 Trust in excess of its target balance (the “Supplemental Trust Target Balance”). If, at the end of any quarter, the Supplemental Trust balance exceeds the Supplemental Trust Target Balance, such excess may be distributed to HG Re. The distribution will be made first as an assignment of accrued interest on the BAM Surplus Notes and second in cash and/or fixed income securities. For the year ended December 31, 2025, HG Re received a distribution from the Supplemental Trust of $61 million, which consisted of an assignment of $30 million of accrued interest on the BAM Surplus Notes and a cash distribution of $31 million. For the year ended December 31, 2024, HG Re received a distribution from the Supplemental Trust of $80 million, which consisted of an assignment of $59 million of accrued interest on the BAM Surplus Notes and a cash distribution of $21 million.

12

As the BAM Surplus Notes are repaid over time, the BAM Surplus Notes will be replaced in the Supplemental Trust by cash and fixed income securities. The Supplemental Trust balance as of December 31, 2025 and 2024 was $607 million and $598 million, which included $323 million and $289 million of cash, investments and accrued investment income, $277 million and $301 million of BAM Surplus Notes at nominal value and $7 million and $8 million of accrued interest receivable on the BAM Surplus Notes at nominal value.

As of December 31, 2025 and 2024, the Collateral Trusts held total assets of $1,007 million and $950 million.

BAM Surplus Notes

Through June 30, 2024, the interest rate on the BAM Surplus Notes was a variable rate equal to the one-year U.S. Treasury rate plus 300 basis points, set annually, with each payment applied pro rata between outstanding principal and interest. Accordingly, in 2024, the interest rate on the BAM Surplus Notes was 8.2% through June 30, 2024. Effective July 1, 2024 and through maturity, HG Global and BAM amended the interest rate on the BAM Surplus Notes to be 10.0%, with a higher proportion of each payment to be applied to outstanding principal.

Under its agreements with HG Global, BAM is required to seek regulatory approval to pay principal and interest on the BAM Surplus Notes only to the extent that its remaining qualified statutory capital and other capital resources continue to support its outstanding obligations, its business plan and its “AA/stable” rating from Standard & Poor’s. No payment of principal or interest on the BAM Surplus Notes may be made without the approval of the NYDFS.

During 2025, HG Global received cash payments of principal and interest on the BAM Surplus Notes totaling $35 million. Of these payments, $24 million was a repayment of principal held in the Supplemental Trust, less than $1 million was a payment of accrued interest held in the Supplemental Trust and $11 million was a payment of accrued interest held outside the Supplemental Trust.

During 2024, HG Global received cash payments of principal and interest on the BAM Surplus Notes totaling $30 million. Of these payments, $21 million was a repayment of principal held in the Supplemental Trust, $1 million was a payment of accrued interest held in the Supplemental Trust and $8 million was a payment of accrued interest held outside the Supplemental Trust.

During 2023, HG Global received a cash payment of principal and interest on the BAM Surplus Notes of $27 million. Of this payment, $18 million was a repayment of principal held in the Supplemental Trust, $2 million was a payment of accrued interest held in the Supplemental Trust and $7 million was a payment of accrued interest held outside the Supplemental Trust.

As of December 31, 2025 and 2024, the principal balance on the BAM Surplus Notes was $277 million and $301 million and total interest receivable on the BAM Surplus Notes was $214 million and $195 million, all at nominal value.

Prior to the deconsolidation of BAM on July 1, 2024, the BAM Surplus Notes, including accrued interest receivable, were classified as intercompany notes carried at nominal value, which eliminated in consolidation. Upon deconsolidation, White Mountains elected the fair value option for the BAM Surplus Notes. As of December 31, 2025 and 2024, the fair value of the BAM Surplus Notes was $339 million and $382 million. The decline was driven by a $38 million decrease in fair value and $35 million in cash payments of principal and interest, partially offset by $30 million of accrued interest. See “BAM Surplus Notes” under “CRITICAL ACCOUNTING ESTIMATES — Fair Value Measurements” on page 88.

Competition/Pricing

Certain sectors of the municipal bond insurance industry are highly competitive. HG Re is only licensed to provide reinsurance to BAM. Accordingly, HG Re, through its reinsurance treaties with BAM, is indirectly exposed to this competition.

BAM’s primary competitor is Assured Guaranty Ltd. (“Assured”). BAM and Assured each seek to differentiate themselves through risk selection, financial strength ratings, claims paying resources and underwriting strategies. BAM believes it has a number of distinct competitive advantages, and that, over time, its mutual structure will deliver a cost of capital advantage relative to its stock company competitor.

Pricing (i.e., premium level) is affected by a number of factors, including interest rate levels, credit spreads, trading value and capture rate (i.e., the percentage of total interest savings captured in the form of insurance premium). All else being equal, pricing is generally higher when interest rates are higher, credit spreads are wider, BAM’s trading value is higher relative to competitors and the capture rate is higher.

13

Insured Portfolio

Under the FLRT, HG Re provides first-loss reinsurance protection of up to 15%-of-par outstanding for each policy assumed from BAM. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds.

The following table presents HG Re’s insured portfolio by asset class as of December 31, 2025 and 2024:

MillionsDecember 31, 2025December 31, 2024

SectorOutstanding Par Value of Policies Assumed
Weighted Average Credit Rating (1)
Outstanding Par Value of Policies Assumed
Weighted Average Credit Rating (1)

General obligation
$10,757.7 A$9,811.0 A

Utility3,079.3 A2,653.3 A

Dedicated tax
2,001.4 A1,858.0 A

General fund
1,709.5 A+1,608.1 A+

Higher education
1,585.3 A-1,363.2 A-

Enterprise systems
1,426.7 A1,209.7 A

Total insured portfolio$20,559.9 A $18,503.3 A

(1) The weighted average credit ratings are based on Standard & Poor’s credit ratings, or if unrated by Standard & Poor’s, the Standard & Poor’s equivalent of credit ratings provided by Moody’s Investor Service (“Moody’s”). HG Re’s weighted average credit rating is calculated using its outstanding par value of policies assumed.

The following tables present HG Re’s ten largest exposures based upon the par value of policies assumed as of December 31, 2025 and 2024:

December 31, 2025

$ in MillionsOutstanding Par Value of Policies AssumedPercent of Total Outstanding Par Value of Policies Assumed
Credit Rating (1)

Metropolitan Transportation Authority (MTA), NY, Mass Transit - Farebox$87.6 0.4 %
A

City of Sherman, TX, (Grayson County), Combined Water & Sewer85.7 0.4
A-

New Jersey Transportation Trust Fund Authority, System & Program

Bonds, NJ, Gas Tax - State84.4 0.4
A

City of Chicago, IL (Cook County)
80.9 0.4
BBB

South Carolina Public Service Authority77.1 0.4 A-

Westfield Washington Schools, IN (Hamilton County)74.5 0.4
AA+

Midway Airport, Chicago City of, IL (Cook County), Airport GARB

(2023 Supplemental Indenture)
73.4 0.4
A

City of Chicago, IL (Cook County), Sales Tax - Local72.5 0.4
A+

Hayward USD, CA (Alameda County)71.0 0.3
A+

O'Hare Airport, IL (Cook County) GARB70.4 0.3
A+

Total of top ten exposures$777.5 3.8 %

(1) The credit ratings are based on Standard & Poor’s credit ratings, or if unrated by Standard & Poor’s, the Standard & Poor’s equivalent of credit ratings provided by Moody’s. “AA+” is the second highest, “A+” is the fifth highest, “A” is the sixth highest, “A-” is the seventh highest and “BBB” is the ninth highest of 23 credit ratings assigned by Standard & Poor’s.

14

December 31, 2024

$ in MillionsOutstanding Par Value of Policies AssumedPercent of Total Outstanding Par Value of Policies Assumed
Credit Rating (1)

Metropolitan Transportation Authority (MTA), NY, Mass Transit - Farebox$79.7 0.4 %A-

Midway Airport, City of Chicago, IL (Cook County), Airport GARB

(2023 Supplemental Indenture)
77.0 0.4 A

City of Sherman, TX, (Grayson County), Combined Water & Sewer76.4 0.4 A

South Carolina Public Service Authority73.1 0.4 A-

City of Chicago, IL (Cook County), Sales Tax - Local71.6 0.4 AA-

New Jersey Transportation Trust Fund Authority, System & Program

Bonds, NJ, Gas Tax - State69.2 0.4 A-

Pennsylvania Turnpike Commission, PA, Toll Roads64.8 0.4 A+

Port Authority of NY and NJ63.0 0.3 AA-

State of Illinois, General Obligation Bonds61.9 0.3 A-

City of Wichita, KS (Sedgwick County), Water & Sewer61.6 0.3 AA-

Total of top ten exposures$698.3 3.7 %

(1) The credit ratings are based on Standard & Poor’s credit ratings, or if unrated by Standard & Poor’s, the Standard & Poor’s equivalent of credit ratings provided by Moody’s. “AA-” is the fourth highest, “A+” is the fifth highest, “A” is the sixth highest and “A-” is the seventh highest of 23 credit ratings assigned by Standard & Poor’s.

The following tables present the geographic distribution of HG Re’s insured portfolio as of December 31, 2025 and 2024:

December 31, 2025

$ in MillionsNumber of RisksOutstanding Par Value of Policies AssumedPercent of Total Outstanding Par Value of Policies Assumed

California908 $3,677.7 17.9 %

Texas1,268 3,388.7 16.5 %

Illinois529 1,909.4 9.3 %

Pennsylvania568 1,718.5 8.4 %

New York423 969.3 4.7 %

New Jersey218 772.3 3.8 %

Alabama221 612.3 3.0 %

Ohio
209 600.4 2.9 %

Florida98 524.0 2.5 %

Indiana158 509.4 2.5 %

Other States1,917 5,877.9 28.5 %

Total insured portfolio6,517 $20,559.9 100.0 %

15

December 31, 2024

$ in MillionsNumber of RisksOutstanding Par Value of Policies AssumedPercent of Total Outstanding Par Value of Policies Assumed

California891 $3,336.9 18.0 %

Texas1,156 2,940.7 15.9

Illinois499 1,721.2 9.3

Pennsylvania555 1,688.2 9.1

New York421 866.3 4.7

New Jersey212 712.7 3.9

Alabama216 563.0 3.0

Florida99 523.3 2.8

Ohio197 494.1 2.7

Indiana152 463.5 2.5

Other States1,753 5,193.4 28.1

Total insured portfolio6,151 $18,503.3 100.0 %

The following table presents HG Re’s insured portfolio by issuer size of exposure as of December 31, 2025 and 2024:

$ in MillionsDecember 31, 2025December 31, 2024

Original Par Value of Policies Assumed Per Issuer (1)
Number of RisksOutstanding Par Value of Policies AssumedPercent of Total Outstanding Par Value of Policies AssumedNumber of RisksOutstanding Par Value of Policies AssumedPercent of Total Outstanding Par Value of Policies Assumed

Less than $1 million2,981 $1,361.8 6.6 %2,796 $1,280.6 6.9 %

$1 to $2 million1,284 1,850.0 9.0 1,260 1,798.8 9.7

$2 to $5 million1,313 4,175.3 20.3 1,242 3,909.2 21.1

$5 to $10 million538 3,800.1 18.5 492 3,430.3 18.5

$10 to $20 million239 3,319.5 16.1 217 2,952.6 16.0

$20 to $50 million131 4,019.5 19.6 121 3,697.8 20.0

Above $50m31 2,033.7 9.9 23 1,434.0 7.8

Total insured portfolio6,517 $20,559.9 100.0 %6,151 $18,503.3 100.0 %

(1) The original par value of policies assumed per issuer does not include refunded and re-issued deals.

Insured Credit Surveillance

HG Re attends BAM’s monthly surveillance committee meetings. The surveillance committee evaluates the credit profile of each insured municipal bond on a periodic basis and places each insured municipal bond into one of four surveillance categories, the last two of which represent insured municipal bonds that are on BAM’s insured credit watchlist. Surveillance category 3 represents insured municipal bonds whose issuers are experiencing financial, legal or administrative issues causing overall credit quality deterioration, but whose probability of generating an insured loss is considered remote. Surveillance category 4 represents insured municipal bonds where a loss is expected or losses have been paid and have not been recovered or are not recoverable. As of December 31, 2025, BAM had assigned one credit to surveillance category 3. BAM has not assigned any credits to surveillance category 4 since inception.

Insured municipal bonds on the watchlist are monitored closely and are subject to BAM’s distressed credit management procedures, including a remediation plan developed in consultation with BAM’s legal counsel and consultants and HG Re. The objectives of any remediation plan are to address the problems the issuer is facing, to address any external factors impacting the credit, to ensure that creditors’ rights are enforced and to cure any breaches that may have occurred with respect to any credit triggers or covenants. BAM may work with other insurers, municipal bondholders and/or interested parties on remediation efforts, as applicable.

16

KUDU

Overview

Kudu provides capital solutions for boutique asset and wealth managers for a variety of purposes including generational ownership transfers, management buyouts, acquisition and growth finance and legacy partner liquidity. Kudu also provides strategic advice to managers from time to time. Kudu’s capital solutions are generally structured as noncontrolling equity interests in the form of revenue and earnings participation contracts (“Participation Contracts”) and designed to generate immediate cash yields.

Kudu expects to fund new capital deployments predominantly through excess operating cash flows, recycling of certain sales transaction proceeds, and available debt capacity, with additional equity contributions from White Mountains and other existing investors as needed.

As of December 31, 2025 and 2024, White Mountains reported $1,402 million and $1,108 million of total assets and $955 million and $792 million of total equity related to Kudu. As of December 31, 2025 and 2024, White Mountains owned 91.2% and 90.4% of Kudu’s basic units outstanding (77.9% and 77.0% on a fully-diluted/fully-converted basis, taking account of management’s equity incentives) and reported $141 million and $128 million of noncontrolling interests related to Kudu.

Portfolio

As of December 31, 2025, Kudu had deployed $1.2 billion, including transaction costs, into 30 asset and wealth management firms globally, including three that have been exited. As of December 31, 2025, Kudu’s asset and wealth management firms had combined assets under management of approximately $153 billion, spanning a range of asset classes including real estate, wealth management, hedge funds, private equity and alternative credit strategies. Since inception, Kudu’s capital was deployed at an initial average gross cash yield of 9.3% based on expected cash in the first year following deployment.

Kudu’s philosophy is to partner with asset and wealth management firms that exhibit strong cash flow generation and growth. Kudu seeks to provide its solutions across a diverse mix of investment strategies and asset classes in the middle market.

Kudu’s average capital deployment to date has been approximately $39 million, with a range from $14 million to $81 million. Apportioned by manager type, Kudu’s portfolio as of December 31, 2025 was deployed 35% in alternatives, 44% in private capital, 14% in wealth management and 7% in traditional asset management. Kudu prioritizes the private capital segment as the underlying clients of these firms tend to be locked-up for an extended period, which can provide stability of revenues in a potential market downturn.

Kudu is geographically diversified with portfolio companies headquartered in the United States and internationally.

17

DISTINGUISHED

Overview

On September 2, 2025, White Mountains acquired a controlling financial interest in Distinguished (the “Distinguished Transaction”). See Note 2 — “Significant Transactions” on page F-19.

Distinguished is a full-service MGA and program administrator for specialty property and casualty insurance. Distinguished places insurance across a diversified portfolio of programs broadly grouped into two verticals. The ScaleCo vertical consists of established programs, primarily focused on real estate and hospitality end markets. The GrowthCo vertical consists of start-up programs, focused on a diversified set of specialty property and casualty insurance products across multiple industries. On behalf of its insurance carrier partners, Distinguished typically manages all aspects of the placement process, including product development, marketing, underwriting and policy issuance. Distinguished earns commissions based on the volume and profitability of the insurance that it places. Distinguished does not retain insurance risk.

As of December 31, 2025, White Mountains reported $735 million of total assets and $428 million of total equity related to Distinguished. As of December 31, 2025, White Mountains owned 55.5% of the basic units outstanding of Distinguished (43.6% on a fully-diluted/fully-converted basis, taking account of management’s equity incentives) and reported $132 million of redeemable noncontrolling interests and $74 million of nonredeemable noncontrolling interests related to Distinguished.

Marketing and Distribution

Distinguished is an MGA and program administrator with delegated binding authorities, and as such, is generally dependent on its carrier partners to bear the insurance risk on the programs designed and underwritten by Distinguished. Distinguished typically expands its programs when market conditions are attractive and shrinks its programs when market conditions are challenging. This practice has led to longstanding insurance carrier partner relationships, in some cases over 20 years. The insurance risk for Distinguished’s programs is supported by 17 insurance carrier partners, with the top three of these carrier partners accounting for 61% of Distinguished’s managed premiums for the year ended December 31, 2025, which includes periods prior to White Mountains’s ownership. White Mountains believes this information is useful in understanding the overall diversification in Distinguished’s capacity.

Distinguished primarily relies on third-party agents and brokers as its sales channel. Substantially all of Distinguished’s products are distributed through third-party agents and brokers who have the principal relationships with policyholders. Agents and brokers have significant influence over renewals, and thus Distinguished’s business model is dependent on its relationships with, and the success of, the agents and brokers with whom Distinguished does business. Distinguished’s programs are supported by over 2,000 agents and brokers, with the top three firms accounting for 10% of Distinguished’s managed premiums for the year ended December 31, 2025, which includes periods prior to White Mountains’s ownership. White Mountains believes this information is useful in understanding the overall diversification in Distinguished’s distribution base.

Competition

Distinguished operates in a highly competitive property and casualty insurance intermediary industry. Competitors are differentiated based on price, conditions of coverage, loss ratio performance, quality of service, technology and other factors. Distinguished’s primary competitors are typically specialty insurance distribution and underwriting businesses and their agents.

Managed Premiums and Commission and Fee Revenues

Managed premiums, which represent the total premiums placed by Distinguished, were $188 million for the period from September 2, 2025, the date of acquisition, through December 31, 2025. The following table presents Distinguished’s managed premiums and commission and fee revenues by vertical for the period from September 2, 2025 through December 31, 2025.

September 2, 2025 - December 31, 2025

MillionsManaged PremiumsCommission and Fee Revenues

ScaleCo
$141.1 $41.3

GrowthCo
46.8 15.4

Total
$187.9 $56.7

18

For the year ended December 31, 2025, Distinguished’s total managed premiums were $568 million, which increased 6% compared to the year ended December 31, 2024. This includes periods prior to White Mountains’s ownership of Distinguished, which White Mountains believes is useful in understanding the overall size and growth in Distinguished’s premium base.

OTHER OPERATIONS

Overview

White Mountains’s Other Operations consists of the Company and its wholly-owned subsidiary, WM Capital, its other intermediate holding companies, its wholly-owned investment management subsidiary, WM Advisors, investment assets managed by WM Advisors, its interests in the Bamboo SPV, MediaAlpha, PassportCard/DavidShield, BroadStreet, Elementum, WTM Partners, Enterprise Solutions, the Bamboo CRVs, Other Operating Businesses and certain other assets.

WM Advisors

As of December 31, 2025, WM Advisors managed and/or provided oversight and administration for substantially all of White Mountains’s fixed maturity investments, short-term investments, common equity securities and other long-term investments.

Bamboo

On January 2, 2024, White Mountains acquired a controlling financial interest in Bamboo. On December 5, 2025, White Mountains completed the sale of a controlling financial interest in WM Pierce Holdings, Inc. and its subsidiaries, including Bamboo MGA (collectively, the "Bamboo Group"), to affiliates of funds advised by CVC Capital Partners (“CVC”), pursuant to the terms of the securities purchase agreement dated October 2, 2025 (the "Bamboo SPA"). Under the terms of the Bamboo SPA, White Mountains sold approximately 77.3% of its equity interest in Bamboo for net cash proceeds at closing of $848 million and retained an indirect equity interest valued at $250 million (the “Bamboo Sale Transaction”). White Mountains’s indirect equity interest is held through the Bamboo SPV. See Note 2 — “Significant Transactions” on page F- 19.

As a result of the Bamboo Sale Transaction, White Mountains deconsolidated the Bamboo Group on December 5, 2025, and Bamboo is no longer a reportable segment. Through December 5, 2025, Bamboo’s results of operations are presented within the Bamboo segment. White Mountains’s noncontrolling equity interest in the Bamboo SPV is accounted for at fair value in other long-term investments within Other Operations. The Bamboo Group’s assets and liabilities have been presented as held for sale as of December 31, 2024. See Note 20 — “Held for Sale” on page F-79.

Bamboo is a capital-light, tech- and data-enabled insurance distribution platform providing homeowners’ insurance and related products to the residential property market in California and, beginning in the third quarter of 2025, in Texas. Bamboo operates primarily through Bamboo MGA, its full-service MGA business, where the company manages all aspects of the placement process on behalf of its fronting and reinsurance carrier partners (“Capacity Providers”), including product development, marketing, underwriting, policy issuance and claims oversight, and it earns commissions based on the volume and profitability of the insurance that it places. Bamboo MGA offers both admitted and non-admitted products. Under its capacity agreements, Bamboo MGA’s commission levels are based on a sliding scale tied primarily to its attritional loss ratio. Bamboo also operates two separate but integrated businesses: (i) a retail agency, within Bamboo MGA, offering ancillary products (e.g., flood, earthquake) on behalf of third parties and (ii) Ide8 Re, Inc. (the “Bamboo Captive”), a U.S.-domiciled captive reinsurer that participates in the underwriting risk of Bamboo’s MGA programs to align interests with Capacity Providers.

As of December 31, 2025, White Mountains had a 27.9% limited partnership interest in the Bamboo SPV. As of December 31, 2025, White Mountains owned 17.2% of the basic units outstanding of Bamboo (14.6% on a fully-diluted/fully-converted basis, taking account of management’s equity incentives) on a look-through basis. As of December 31, 2025, the fair value of White Mountains’s interest in the Bamboo SPV was $250 million.

19

MediaAlpha

MediaAlpha is a marketing technology company. It operates a transparent and efficient customer acquisition technology platform that facilitates real-time transactions between buyers and sellers of consumer referrals (i.e., clicks, calls and leads), primarily in the property & casualty, health and life insurance verticals. MediaAlpha generates revenue by earning a fee for each consumer referral sold on its platform. A transaction becomes payable only on a qualifying consumer action, and is not contingent on the sale of a product to the consumer.

White Mountains’s investment in MediaAlpha is accounted for at fair value based on the publicly traded share price of MediaAlpha’s common stock and is presented as a separate line item on the balance sheet.

During the second quarter of 2024, MediaAlpha completed a secondary offering of 7.6 million shares at $19.00 per share ($18.24 per share net of underwriting fees). In the secondary offering, White Mountains sold 5.0 million shares for net proceeds of $91.2 million. During the second quarter of 2023, White Mountains completed a tender offer to purchase 5.9 million additional shares of MediaAlpha at a purchase price of $10.00 per share.

As of December 31, 2025, White Mountains owned 17.9 million shares of MediaAlpha, representing a 27.4% basic ownership interest based on the total class A and class B common shares outstanding in MediaAlpha’s Report on Form 10-Q dated October 29, 2025. At the December 31, 2025 share price of $12.95, the fair value of White Mountains’s investment in MediaAlpha was $231 million. As of December 31, 2024, White Mountains owned 17.9 million shares of MediaAlpha, representing a 26.6% basic ownership interest. At the December 31, 2024 share price of $11.29, the fair value of White Mountains’s investment in MediaAlpha was $202 million.

PassportCard/DavidShield

PassportCard/DavidShield is an international MGA specializing in leisure travel insurance and global expatriate medical insurance. PassportCard/DavidShield delivers digitally-enabled insurance solutions that provide real time funding for covered medical expenses at the point of care.

PassportCard/DavidShield writes two principal product lines: (i) leisure travel insurance (“PassportCard”) and (ii) comprehensive expatriate medical services (“DavidShield”). PassportCard/DavidShield offers these products to both individuals and organizations. Its principal markets include Israel (its home market) as well as the European Union and Australia – servicing over two million insured members in over 180 countries. In Israel, PassportCard/DavidShield operates through a wholly-owned insurance carrier that underwrites policies and cedes substantially all underwriting risk to its highly-rated reinsurance partners. Outside Israel, PassportCard/DavidShield places policies with licensed third-party insurance carriers. PassportCard/DavidShield earns commissions for the placement of policies with its insurance and reinsurance carrier partners and licensing fees for the use of its card-based technology. PassportCard/DavidShield distributes its products through brokers, strategic partnerships and direct-to-consumer digital channels.

There are a number of distinct advantages to the PassportCard/DavidShield insurance solutions that differentiate its business in the marketplace. PassportCard/DavidShield offers its members a proprietary, card-based platform that enables paperless claims processing and immediate payment authorization, reducing reliance on traditional reimbursement models. This technology-driven approach supports enhanced claims control, fraud mitigation and data-informed loss management, thereby contributing to competitive loss ratios for its reinsurance partners and a differentiated customer experience.

By leveraging the regulated payment capabilities and propriety infrastructure of a debit card model, PassportCard/DavidShield has been able to integrate its insurance services with personal travel-related payment functionality. In July 2025, PassportCard/DavidShield launched an integrated Travel Money Payment Card, a solution combining the insurance claims card with a personal travel-focused payment card that enables customers to manage both medical expenses and personal travel spending through the same card.

As a business based in Israel, PassportCard/DavidShield has been affected by the geopolitical environment in the Middle East. Following the events of October 7, 2023 and the resulting war in Gaza, PassportCard/DavidShield experienced a significant decline in revenues relating to its Israeli leisure travel segment. However, Israeli leisure travel revenues placed by PassportCard have gradually recovered and have now surpassed pre-war levels despite intermittent periods of increased geopolitical unrest in the region and reduced capacity from international airline carriers offering service to and from Israel. Meanwhile, the comprehensive expatriate medical insurance placed by DavidShield has remained largely unaffected by the geopolitical environment.

White Mountains’s noncontrolling equity interest in PassportCard/DavidShield is accounted for at fair value within other long-term investments. As of December 31, 2025 and 2024, White Mountains owned 53.8% basic ownership interest of PassportCard/DavidShield (51.5% on a fully-diluted/fully-converted basis). As of December 31, 2025 and 2024, the fair value of White Mountains’s interest in PassportCard/DavidShield was $170 million and $150 million.

20

BroadStreet

BroadStreet is an insurance brokerage company with a presence in all 50 U.S. states and ten Canadian provinces. BroadStreet focuses on commercial and personal property & casualty insurance and employee benefits. BroadStreet partners with leading insurance agencies, known as core agency partners. Complementing its M&A capabilities and capital solutions, BroadStreet provides a vast network of market resources, tools and expertise to its core agency partners, working alongside them to drive organic growth and improve agency performance.

On July 18, 2025, White Mountains invested $150 million into BroadStreet through the BroadStreet SPV, alongside co-lead investors Ethos Capital LP and British Columbia Investment Management Corporation. See Note 2 — “Significant Transactions” on page F- 19. White Mountains’s noncontrolling equity interest in the BroadStreet SPV is accounted for at fair value using NAV as a practical expedient and is included within other long-term investments. As of December 31, 2025, the fair value of White Mountains’s interest in the BroadStreet SPV was $160 million. As of December 31, 2025, White Mountains had a 10.9% limited partnership interest in the BroadStreet SPV and a less than 5% ownership of BroadStreet on a look-through basis.

Elementum

Elementum is a third-party registered investment adviser specializing in natural catastrophe insurance-linked securities (“ILS”). Elementum manages separate accounts and pooled investment vehicles across various ILS sectors, including catastrophe bonds, collateralized reinsurance investments and industry loss warranties on behalf of third-party clients.

White Mountains has a noncontrolling equity interest in Elementum, which is accounted for at fair value within other long-term investments. As of December 31, 2025 and 2024, the fair value of White Mountains’s interest in Elementum totaled $35 million. As of December 31, 2025 and 2024, White Mountains had a 26.6% limited partnership interest in Elementum (25.4% on a fully-diluted/fully-converted basis).

White Mountains also has investments in ILS funds managed by Elementum. As of December 31, 2025 and 2024, White Mountains had $50 million and $74 million invested in ILS funds managed by Elementum.

WTM Partners

In October 2023, White Mountains announced the launch of WTM Partners, which will acquire businesses in non-insurance, non-financial services sectors including essential services, light industrial and specialty consumer. White Mountains expects to deploy up to $500 million of equity capital through WTM Partners over time. WTM Partners deployed $58 million in Enterprise Solutions in 2025, which was the first acquisition by WTM Partners. WTM Partners did not deploy any equity capital in 2024.

Enterprise Solutions

On April 1, 2025, White Mountains acquired a controlling financial interest in Enterprise Solutions (the “Enterprise Solutions Transaction”). See Note 2 — “Significant Transactions” on page F- 19. Enterprise Solutions provides specialty electrical contracting services to commercial and institutional customers. As of December 31, 2025, White Mountains reported $178 million of total assets and $90 million of total equity related to Enterprise Solutions. As of December 31, 2025, White Mountains owned 65.5% of Enterprise Solutions on a basic units outstanding basis (59.0% on a fully-diluted/fully-converted basis, taking account of management’s equity incentives) and reported $31 million of noncontrolling interests.

21

Bamboo CRVs

The Bamboo CRVs are special purpose collateralized reinsurance vehicles that provide reinsurance capacity to Bamboo. White Mountains capitalized the Bamboo CRVs by purchasing preference shares that were deposited into collateral trust accounts. The Bamboo CRVs entered into collateralized quota share agreements with certain of Bamboo’s fronting partners to provide reinsurance protection on Bamboo’s admitted and non-admitted business written in the 2025 and 2024 treaty years. As of December 31, 2025, White Mountains’s total commitment to the Bamboo CRVs was $10 million.

Other Operating Businesses

White Mountains has controlling equity interests in various other operating businesses which are consolidated. As of December 31, 2025, White Mountains reported $87 million of total assets, $54 million of total equity (net of intercompany eliminations) and $6 million of noncontrolling interests related to these businesses. As of December 31, 2024, White Mountains reported $100 million of total assets, $65 million of total equity (net of intercompany eliminations) and $9 million of noncontrolling interests related to these businesses.

White Mountains also has noncontrolling equity interests in various other operating businesses, which are generally accounted for at fair value within other long-term investments. As of December 31, 2025 and 2024, the fair value of these interests totaled $58 million and $49 million.

INVESTMENTS

White Mountains’s investment philosophy is to maximize long-term, after-tax total returns while taking prudent levels of risk and maintaining a diversified portfolio, subject to White Mountains’s investment guidelines and various regulatory restrictions. Under White Mountains’s investment philosophy, each dollar of after-tax investment income or investment gains (realized or unrealized) is valued equally. White Mountains’s investment philosophy also incorporates Environmental, Social and Governance (“ESG”) considerations. For investment assets actively managed by WM Advisors, thorough credit risk assessments are conducted, utilizing Nationally-Recognized Statistical Rating Organizations research and ratings. For actively managed investment assets sub-advised to third-party registered investment managers, White Mountains only utilizes managers who incorporate ESG factors into their investment processes.

White Mountains maintains a fixed income portfolio that consists primarily of high-quality, short-duration, fixed maturity investments and short-term investments. White Mountains invests in fixed maturity investments that are attractively priced in relation to their investment risks and actively manages the average duration of the fixed income portfolio. As of December 31, 2025, the fixed income portfolio duration, including short-term investments, was 1.5 years. White Mountains has established relationships with select third-party registered investment advisers to manage a portion of its fixed income portfolio.

White Mountains maintains an equity portfolio that consists of common equity securities, its investment in MediaAlpha and other long-term investments. As of December 31, 2025, White Mountains’s portfolio of common equity securities generally consists of international listed equity funds and passive exchange traded funds (“ETFs”). White Mountains’s other long-term investments consist primarily of unconsolidated entities, including Kudu’s Participation Contracts, the Bamboo SPV, PassportCard/DavidShield and the BroadStreet SPV, as well as private equity funds and hedge funds, a bank loan fund and Lloyd’s trust deposits. See “Portfolio Composition” on page 76.

22

REGULATION

United States

Insurance Regulation

Distinguished is licensed in all 50 states as an insurance producer. The distribution of insurance products is a heavily regulated industry subject to regulation and supervision by state regulatory authorities. State insurance laws are often complex and generally grant broad discretion to supervisory authorities in adopting regulations and supervising regulated activities, which generally includes the licensing of insurance brokers and agents, intermediaries and third-party administrators. Our continuing ability to distribute insurance products in the states in which we currently operate is dependent upon our compliance with the rules and regulations promulgated by the regulatory authorities in each of these states.

White Mountains believes that Distinguished is in compliance with all applicable laws and regulations pertaining to its business that would have a material effect on its financial condition or results of operations in the event of non-compliance.

Rate Regulations

Nearly all states have insurance laws requiring personal property and casualty insurers to file rating plans, policy or coverage forms and other information with the state’s regulatory authority. In many cases, such rating plans and/or policy or coverage forms must be approved by the regulatory authority prior to use. The speed with which an insurer can change rates in response to competition or in response to increasing costs depends, in part, on whether the rating laws are (i) prior approval, (ii) file-and-use or (iii) use-and-file laws. In states with prior approval laws, the regulator must approve a rate before the insurer may use it. In states with file-and-use laws, the insurer does not have to wait for the regulator’s approval to use a rate, but the rate must be filed with the regulatory authority prior to being used. In states with use-and-file laws, the insurer must file rates within a certain period after the insurer begins to use them. Under all three types of rating laws, the regulator has the authority to disapprove a rate filing. While Distinguished is not an insurer, and thus not required to file its own rating plans with the state's regulatory authority, Distinguished’s commissions are derived from a percentage of the premium rates set by its insurance carrier partners in conjunction with state law, and the sustainability of Distinguished’s business is dependent on such rates.

Premium Accounts Held in Trust

Distinguished maintains trust accounts in order to comply with fiduciary requirements under U.S. state insurance laws and regulations relating to premium trust accounts. Under such laws, insurance agencies that do not make immediate remittances to counterparties (such as insurance companies, clients or other producers to which premium, commissions or other amounts are due from time to time) must segregate funds owed to such counterparties, and these funds must be held in trust for the insurance company, client or other relevant third-party payee. Distinguished’s use of trust accounts is routinely subject to audits by its insurance carrier partners and other external auditors.

Cybersecurity

Certain of our U.S. operations are subject to federal and state cybersecurity and data privacy laws, including the California Consumer Privacy Act, as amended by the California Privacy Rights Act, and the NYDFS Cybersecurity Regulation. These laws impose requirements relating to the protection of personal information, breach notification, governance, risk management and certification. Compliance with these requirements may increase operating costs, and violations may result in regulatory penalties, litigation and reputational harm.

Investment Regulation

Kudu Investment Holdings, LLC, a subsidiary of Kudu, is an investment adviser that is registered with the SEC under Section 203 of the United States Investment Advisers Act of 1940.

23

Bermuda

Insurance Regulation

The Insurance Act 1978 of Bermuda and related regulations, as amended (the “Insurance Act”), regulates the insurance

business of HG Re, a special purpose insurer, GAIL, Ark’s wholly-owned Class 4 insurance and reinsurance company and Outrigger Re Ltd., a special purpose insurer. Outrigger Re Ltd. is also registered as a segregated accounts company under the Bermuda Segregated Accounts Companies Act 2000, as amended (the “SAC Act”). The Insurance Act provides that no person may carry on any insurance business in or from within Bermuda unless registered as an insurer under the Insurance Act by the Bermuda Monetary Authority (“BMA”). The BMA, in deciding whether to grant registration, has broad discretion to act as it thinks fit in the public interest. From time to time, HG Re, GAIL and Outrigger Re Ltd. may apply for, and be granted, certain modifications to, or exemptions from, regulatory requirements, which may otherwise apply to them.

The Insurance Act imposes solvency and liquidity standards as well as auditing and reporting requirements and confers on the BMA powers to supervise, investigate and intervene in the affairs of insurance companies. The SAC Act stipulates its own solvency test for the declaration of dividends and distributions for segregated accounts, which takes into account the solvency of each segregated account individually, rather than the solvency of the company itself.

Classification

GAIL is registered as a Class 4 insurer. Class 4 insurers carry on general insurance business including excess liability business or property catastrophe, marine & energy, casualty and specialty reinsurance business and have a total statutory capital and surplus of not less than $100 million.

As special purpose insurers, HG Re and Outrigger Re Ltd. are insurers that carry on special purpose business. Special purpose business under the Insurance Act is insurance business under which an insurer fully collateralizes its liabilities to the insured persons through (i) the proceeds of any one or more of (a) a debt issuance where the repayment rights of the providers of such debt are subordinated to the rights of the person insured or (b) some other financing mechanism approved by the BMA; (ii) cash; and (iii) time deposits. Special purpose insurers may be registered to carry on either restricted special purpose business or unrestricted special purpose business. Restricted special purpose business is special purpose business conducted between a special purpose insurer and specific insureds approved by the BMA. Both HG Re and Outrigger Re Ltd. are only able to carry on restricted purpose business.

Capital and Solvency Return

As a Class 4 insurer, GAIL is required to file, on an annual basis, a capital and solvency return in respect of its general business, which currently includes, among other items, a statutory economic balance sheet, a schedule of risk management, a catastrophe risk return, a schedule of loss triangles or reconciliation of net loss reserves (where applicable), a schedule of eligible capital and the Enhanced Capital Requirement (“ECR”) as calculated by the Bermuda Solvency and Capital Requirement (“BSCR”) model (or an approved internal model). The BSCR is a mathematical model designed to give the BMA robust methods for determining an insurer’s capital adequacy. Underlying the BSCR is the belief that all insurers should operate on an ongoing basis with a view to maintaining their capital at a prudent level in excess of the minimum solvency margin otherwise prescribed under the Insurance Act. The 2025 BSCR must be filed with the BMA before April 30, 2026; at this time, we believe GAIL will exceed the minimum amount required to be maintained under Bermuda law.

As special purpose insurers, HG Re and Outrigger Re Ltd. are also required to file annually with the BMA a statutory return which includes, among other matters, the statutory financial statements, a statement of control and changes of control, a solvency certificate, an annual statutory declaration, an own-risk assessment, alternative capital arrangements report, cyber risk management report and compliance with sanctions report.

Financial Condition Report

As a Class 4 insurer, GAIL is required to prepare and publish a financial condition report (“FCR”), which provides, among other things, details of measures governing the business operations, corporate governance framework and solvency and financial performance of the insurer/insurance group. The FCR will be made available in accordance with the requirements of the Insurance Act.

As special purpose insurers, HG Re and Outrigger Re Ltd. are not subject to this requirement.

24

Minimum Solvency Margin

As a general business insurer, GAIL is required to maintain statutory assets in excess of its statutory liabilities by an amount, equal to or greater than the prescribed minimum solvency margin. The minimum solvency margin that must be maintained by a Class 4 insurer is the greater of (i) $100 million, (ii) 50% of net premiums written (with a credit for reinsurance ceded not exceeding 25% of gross premiums), (iii) 15% of net aggregate loss and loss expense provisions and other insurance reserves or (iv) 25% of the ECR.

As special purpose insurers, HG Re and Outrigger Re Ltd. must maintain a minimum solvency margin whereby their special purpose business assets must exceed their special purpose business liabilities by at least $1.

Enhanced Capital Requirement

As a Class 4 insurer, GAIL is required to maintain its available statutory economic capital and surplus at a level at least equal to its ECR. The ECR must at all times equal or exceed the insurer’s minimum solvency margin and may be adjusted in circumstances where the BMA concludes that the insurer’s risk profile deviates significantly from the assumptions underlying its ECR or the insurer’s assessment of its risk management policies and practices used to calculate the ECR applicable to it. While not specifically referred to in the Insurance Act, the BMA has also established a target capital level for each Class 4 insurer equal to 120% of the respective ECR. While a Class 4 insurer is not currently required to maintain its statutory economic capital and surplus at this level, the target capital level serves as an early warning tool for the BMA and failure to maintain statutory capital at least equal to the target capital level will likely result in increased BMA regulatory oversight.

As special purpose insurers, HG Re and Outrigger Re Ltd. are not subject to this requirement.

Minimum Liquidity Ratio

The Insurance Act provides a minimum liquidity ratio for general business insurers such as GAIL. An insurer engaged in general business is required to maintain the value of its relevant assets at not less than 75% of the amount of its relevant liabilities. Relevant assets include, but are not limited to, cash and time deposits, quoted investments, unquoted bonds and debentures, investment income due and accrued, accounts and premiums receivable, insurance and reinsurance balances receivable and funds held by ceding reinsurers. Relevant liabilities include, but are not limited to, general business insurance reserves and total other liabilities less deferred income tax and sundry liabilities, letters of credit and guarantees.

As special purpose insurers, HG Re and Outrigger Re Ltd. are not subject to this requirement.

Eligible Capital

As a Class 4 insurer, GAIL must maintain available capital in accordance with a “three-tiered capital system” to enable the BMA to better assess the quality of an insurer’s capital resources. All capital instruments are classified as either basic or ancillary capital, which in turn are classified into one of three tiers (Tier 1, Tier 2 and Tier 3) based on their “loss absorbency” characteristics. Eligibility limits are then applied to each tier in determining the amounts eligible to cover regulatory capital requirement levels. Under this regime, not more than certain specified percentages of Tier 1, Tier 2 and Tier 3 capital may be used to satisfy the Class 4 insurers' minimum solvency margin, ECR requirements and target capital level.

As special purpose insurers, HG Re and Outrigger Re Ltd. are not subject to this requirement.

Restrictions on Dividends and Reductions of Capital

As a Class 4 insurer, GAIL is prohibited from declaring or paying any dividends if in breach of the required minimum solvency margin or minimum liquidity ratio (the “Relevant Margins”) or if the declaration or payment of such dividend would cause the insurer to fail to meet the Relevant Margins. Further, Class 4 insurers are prohibited from declaring or paying in any financial year dividends of more than 25% of its total statutory capital and surplus (as shown on its previous financial year’s statutory balance sheet) unless it files (at least seven days before payment of such dividends) with the BMA an affidavit stating that it will continue to meet its Relevant Margins. Class 4 insurers must obtain the BMA’s prior approval for a reduction of 15% or more of the total statutory capital as set forth in its previous year’s financial statements. These restrictions on dividends under the Insurance Act are in addition to the solvency requirements under the Companies Act 1981 of Bermuda, as amended (the “Companies Act”). See “LIQUIDITY AND CAPITAL RESOURCES — Dividend Capacity” on page 81 for further discussion.

As special purpose insurers, HG Re and Outrigger Re Ltd. are not required to obtain the BMA’s prior approval in connection with any reduction of total statutory capital but are prohibited from declaring or paying a dividend if they are in breach of their minimum solvency margin or if the declaration or payment of such dividend would cause such a breach. The solvency test for the declaration of dividends by WM Outrigger Re, as a segregated account, is evaluated based upon the solvency of WM Outrigger Re, rather than the solvency of Outrigger Re Ltd. as a whole.

25

Insurance Code of Conduct and Insurance Sector Operational Cyber Risk Management Code of Conduct

All Bermuda insurers are required to comply with the BMA’s Insurance Code of Conduct, which establishes duties, requirements and standards to be complied with to ensure each insurer implements sound corporate governance, risk management and internal controls. Failure to comply with these requirements will be a factor taken into account by the BMA in determining whether an insurer is conducting its business in a sound and prudent manner under the Insurance Act and, in the case of GAIL, in calculating the operational risk charge applicable in accordance with the insurer's BSCR model (or an approved internal model).

All Bermuda insurers are also required to comply with the BMA’s Insurance Sector Operational Cyber Risk Management Code of Conduct, which establishes duties, requirements and standards to be complied with by each insurer in relation to operational cyber risk management.

Powers of Investigation, Intervention and Obtaining Information

The BMA has certain powers of investigation and intervention relating to insurers and their holding companies, subsidiaries and other affiliates, which it may exercise in the interest of such insurer’s policyholders or if there is any risk of insolvency or of a breach of the Insurance Act or the insurer’s license conditions. The BMA may cancel an insurer’s registration on certain grounds specified in the Insurance Act.

Notification of Cyber Reporting Events

Every insurer subject to the Insurance Act must notify the BMA of certain cybersecurity events and provide follow-up reporting. Failure to comply may result in regulatory action.

Policyholder Priority

In the event of a liquidation or winding up of an insurer, policyholders’ liabilities receive payment ahead of general unsecured creditors. Subject to the prior payment of preferential debts under the Employment Act 2000 and the Companies Act, the insurance debts of an insurer must be paid in priority to all other unsecured debts of the insurer.

Certain Other Bermuda Law Considerations

The Company is an exempted company registered under the Companies Act. As a result, the Company is required to comply with the provisions of the Companies Act regulating the payment of dividends and making of distributions from contributed surplus. A company is prohibited from declaring or paying a dividend, or making a distribution out of contributed surplus, if there are reasonable grounds for believing that:

(1) the company is, or would after the payment be, unable to pay its liabilities as they become due; or

(2) the realizable value of the company’s assets would thereby be less than its liabilities.

In addition, the Companies Act regulates return of capital, reduction of capital and any purchase or redemption of shares by the Company.

The Economic Substance Act 2018, as amended (“ESA”) impacts every Bermuda registered entity engaged in a “relevant activity,” requiring impacted entities to maintain a substantial economic presence in Bermuda and to satisfy economic substance requirements. Under the ESA, insurance or holding entity activities (both as defined in the ESA and the Economic Substance Regulations 2018, as amended) are relevant activities. To the extent that the ESA applies to any of our Bermuda entities, we are required to demonstrate compliance with economic substance requirements by filing an annual economic substance declaration with the Bermuda Registrar of Companies. Any entity that must satisfy economic substance requirements but fails to do so could face automatic disclosure to competent authorities in the European Union of the information filed by the entity with the Bermuda Registrar of Companies in connection with the economic substance requirements. Additionally, a company may also face penalties, restrictions or regulation of its business activities and may be struck off as a registered entity in Bermuda for failure to satisfy economic substance requirements. The Company believes it complies with all of the applicable laws and regulations pertaining to economic substance that would have a material effect on its financial condition and results of operations in the event of non-compliance.

26

United Kingdom

PRA and FCA Regulation

As an insurer in the United Kingdom, Ark is dual-regulated by the Financial Conduct Authority (the “FCA”) and the Prudential Regulation Authority (the “PRA”) (collectively, the “U.K. Regulators”). The PRA currently has ultimate responsibility for the prudential supervision of financial services in the United Kingdom. The FCA has responsibility for market conduct regulation. The U.K. Regulators regulate insurers, insurance intermediaries and Lloyd’s. Both the PRA and FCA have substantial powers of intervention in relation to regulated firms.

Lloyd’s Regulation

Lloyd’s as a whole is authorized by the PRA and regulated by both the FCA and the PRA. Lloyd’s is required to implement certain rules prescribed by the PRA and by the FCA; such rules are to be implemented by Lloyd’s pursuant to its powers under the Lloyd’s Act 1982 relating to the operation of the Lloyd’s market. Lloyd’s prescribes, in respect of its managing agents and corporate and individual members, certain minimum standards relating to their management and control, solvency and various other requirements. If it appears to either the PRA or the FCA that either Lloyd’s is not fulfilling its delegated regulatory responsibilities or that managing agents are not complying with the applicable regulatory rules and guidance, the PRA or the FCA may intervene at their discretion.

Lloyd’s permits its members to underwrite insurance risks through Lloyd’s syndicates. Members of Lloyd’s may participate in a syndicate for one or more underwriting year(s) by providing capital to support the syndicate’s underwriting. All syndicates are managed by Lloyd’s approved managing agents. Managing agents receive fees and profit commissions in respect of the underwriting and administrative services they provide to the syndicates.

General

The operations of ASML, Ark’s wholly-owned Lloyd’s managing agent, are subject to oversight by Lloyd’s, through the Lloyd’s Council. ASML’s business plan for the Syndicates, including maximum stamp capacity, requires annual approval from Lloyd’s. Stamp capacity is a measure of the amount of net premium (premiums written less acquisition costs) that a syndicate is authorized by Lloyd’s to write. Lloyd’s may require changes to any business plan presented to it or additional capital to be provided to support the underwriting plan. Lloyd’s approved stamp capacity in 2026 for Syndicate 4020, including ACSN 3832, is £850 million ($1,148 million based upon the foreign currency exchange spot rate as of December 31, 2025) and for Syndicate 3902 is £250 million ($338 million based upon the foreign currency exchange spot rate as of December 31, 2025). The Syndicates are supported by capital provided through ACML, Ark’s wholly-owned Lloyd’s corporate member.

Ark has deposited certain assets with Lloyd’s to support ACML’s underwriting business at Lloyd’s. Dividends from a Lloyd’s managing agent or a member of Lloyd’s can be declared and paid provided the relevant syndicate has sufficient profits available for distribution subject to Lloyd’s solvency requirements. By entering into a membership agreement with Lloyd’s, ACML has undertaken to comply with all Lloyd’s bye-laws and regulations as well as the provisions of the Lloyd’s Acts and the Financial Services and Markets Act 2000, as amended by the Financial Services Act 2012.

Capital Requirements

The underwriting capacity of a member of Lloyd’s must be supported by a deposit in the form of cash, securities or letters of credit in an amount determined under the capital adequacy regime of the U.K.’s PRA. The amount of such deposit is calculated for each member through the completion of an annual capital adequacy exercise. Under these requirements, Lloyd’s must demonstrate that each member has sufficient assets to meet its underwriting liabilities plus a required solvency margin. The required amount of Funds at Lloyd’s is determined by Lloyd’s based on each syndicate’s solvency and capital requirement as calculated through its internal model.

Intervention Powers

The Lloyd’s Council has wide discretionary powers to regulate members’ underwriting at Lloyd’s. It may, for instance, withdraw a member’s permission to underwrite business or to underwrite a particular class of business. The Lloyd’s Council may change the basis on which syndicate expenses are allocated or vary the Funds at Lloyd’s requirements or the investment criteria applicable to the provision of Funds at Lloyd’s. Exercising any of these powers might affect the return on the member’s participation in a given underwriting year. If a member of Lloyd’s is unable to pay its debts to policyholders, the member may obtain financial assistance from the Lloyd’s Central Fund, which in many respects acts as an equivalent to a state guaranty fund in the United States. If Lloyd’s determines that the Central Fund needs to be increased, it has the power to assess premium levies on current members of Lloyd’s. The Lloyd’s Council has discretion to call or assess up to 3% of a member’s underwriting capacity in any one year as a Central Fund contribution.

While not currently material to Ark’s operations, the Syndicates also access insurance business from the European Economic Area through the London Branch of Lloyd’s Insurance Company. Lloyd’s Insurance Company is authorized and regulated by the National Bank of Belgium and regulated by the Financial Services and Markets Authority.

27

U.K. Domestic Prudential Regime

Following the United Kingdom’s exit from the European Union, U.K.-authorized insurers are subject to the U.K.’s domestic prudential regime administered by the PRA. The regime, which evolved from the EU Solvency II framework, establishes risk-based capital and governance requirements. Lloyd’s must satisfy PRA solvency requirements based on its internal model, and Ark’s underwriting capacity at Lloyd’s is subject to these PRA and Lloyd’s capital standards.

Cybersecurity

Ark is subject to U.K. data protection laws, including the U.K. General Data Protection Regulation and the Data Protection Act 2018, and, where applicable, the EU General Data Protection Regulation. These laws impose requirements relating to the processing of personal data, including breach notification, data subject rights, governance controls and restrictions on cross-border data transfers. Violations may result in significant administrative fines and other regulatory action.

Climate Change

In response to PRA climate change risk management guidelines, Ark has established a climate change working group and has undertaken a climate change risk assessment. The risk assessment highlighted regulatory, claims, underwriting and investment risks associated with climate change. Ark regularly analyzes climate change risk as part of its risk management framework. Ark also engages with industry peers through the Lloyd’s Climate Change market group. Ark has assigned its Chief Risk Officer responsibility under the PRA Senior Insurance Managers Regime for climate change risk. The Chief Risk Officer reports to the Ark Board on climate change matters.

General

Change of Control

The jurisdictions in which White Mountains operates have laws and regulations that require regulatory approval of a change of control. Where such laws apply, there can be no effective change in our control (or in the control of some or our subsidiaries) unless the person seeking to acquire control has filed a statement with the regulators and obtained prior approval for the proposed change.

RATINGS

Insurance companies are evaluated by various rating agencies in order to measure each company’s financial strength. Higher ratings generally indicate stronger financial stability and claims paying ability. White Mountains believes that strong ratings are important factors in the marketing and sale of insurance products and services to agents, consumers and ceding companies.

As of February 27, 2026, each of Lloyd’s Syndicates 4020 and 3902 benefits from the financial strength rating of “A+/stable” by A.M. Best Company, Inc. (“A.M. Best”) and “AA-/stable” by Standard & Poor’s assigned to the Lloyd’s marketplace. “A+” is the second highest of 16 financial strength ratings assigned by A.M. Best and “AA-” is the fourth highest of 23 financial strength ratings assigned by Standard & Poor’s.

As of February 27, 2026, GAIL’s financial strength rating was “A/stable” by A.M. Best. “A” is the third highest of 16 financial strength ratings assigned by A.M. Best.

HUMAN CAPITAL

As of December 31, 2025, White Mountains employed 1,648 people (consisting of 85 people at the Company, WM Capital, its other intermediate holding companies, WM Advisors, WTM Partners and HG Global, 300 people at Ark, 17 people at Kudu, 288 people at Distinguished and 958 people at its consolidated Other Operating Businesses).

White Mountains’s strength lies in its people, and it proactively supports each employee’s well-being and development. The Company’s Board of Directors receives periodic reporting on employee satisfaction and concerns and interacts with employees across White Mountains. White Mountains has an inclusive, team-oriented culture in which all employees are treated with respect. Under the guidelines of the Company’s Code of Business Conduct, it is firmly committed to providing equal employment opportunities. White Mountains values diversity of backgrounds, experiences and ideas, which it believes fosters more engaging discussions, stronger collaboration and better company performance. White Mountains invests in the professional development of its workforce and is committed to the long-term development of its workforce and the cultivation of its next generation of leaders.

28