Hamilton Insurance Group, Ltd.

The estimated reserve for losses and loss adjustment expenses ("loss reserves") represents management’s best estimate of the unpaid portion of the Company’s ultimate liability for losses and loss adjustment expenses for insured and reinsured events that have occurred at or before the balance sheet date, based on its assessment of facts and circumstances known at that particular point in time. Loss reserves reflect both claims that have been reported to the Company ("case reserves") and claims that have been incurred but not reported to the Company ("IBNR").

Loss reserves are complex estimates, not an exact calculation of liabilities. Management reviews loss reserve estimates at each quarterly reporting date and considers all significant facts and circumstances known at that particular point in time. As additional experience and other data becomes available and/or laws and legal interpretations change, management may adjust previous estimates. Adjustments are recognized in the period in which they are determined and may impact that period's underwriting results either favorably (when current estimates are lower than previous estimates) or unfavorably (when current estimates are higher than previous estimates).

Gross loss reserves for each of the reportable segments, segregated between case reserves and IBNR, by reserve class, are shown below:

Case Reserves

With respect to insurance business, the Company is generally notified of losses by brokers and/or insureds. The Company’s claims personnel use this and other relevant information to estimate ultimate covered losses arising from the claim, including the cost of claims adjustment administration and settlement, including any legal or other fees. These estimates reflect the judgment of the Company’s claims personnel based on their experience and knowledge, the nature of the specific claim and, where appropriate, the advice of legal counsel, third party claims administrators and loss adjusters. In syndicated markets, such as Lloyd’s, the Company’s case reserves may also be based in part on information provided by the lead insurer.

With respect to reinsurance business, the Company is typically notified of losses by brokers and/or ceding companies. For excess of loss contracts, the Company is typically notified of insured losses on specific contracts in the form of an individual loss notification and records a case reserve for the estimated ultimate liability arising from the claim. For contracts written on a proportional basis, the Company typically receives aggregated claims information in the form of a loss bordereaux and records a case reserve for the estimated ultimate liability arising from the claim based on that information. Proportional reinsurance contracts typically require that losses in excess of pre-defined amounts be separately notified so that the Company can adequately evaluate them. The Company’s claims department evaluates each specific loss notification received and, based on their knowledge and experience, may record additional case reserves when a ceding company’s reserve for a claim is considered inadequate. The Company also undertakes cedant audits, using outsourced legal and industry experience where necessary. This allows the Company to review different cedants’ claims handling practices, understand the level of prudence employed by different cedants and ensure that reserves are consistent with exposures, adequately established, and properly reported in a timely manner.

IBNR

IBNR estimates are necessary due to the potential development on reported claims and the reporting time lag between when a loss event occurs and when it is actually reported (the "reporting lag"). Reporting lags may arise from a number of factors, including but not limited to the nature of the loss, the use of intermediaries and the complexity of the claims adjusting process. The lack of specific information means the Company must make estimates. IBNR is calculated by deducting incurred losses (i.e. paid losses and case reserves) from management’s best estimate of the ultimate losses. Unlike case reserves, which are established at the claim or contract level, IBNR reserves are generally established at an aggregate level and cannot be identified as reserves for a particular loss event or contract.

Reserving Methodology

When conducting actuarial analysis, management organizes the Company’s recorded reserves into exposure groupings based on reasonably homogeneous loss development characteristics, underwriting years and reserving classes. Management periodically reviews the exposure groupings and may make changes to the groupings over time as the Company’s business changes.

The actuarial methodologies used to perform the quarterly reserving analysis that determines our estimate of the ultimate reserve for losses and loss adjustment expenses for each exposure group include:

•Initial expected loss ratio ("IELR") method: The IELR method calculates an estimate of ultimate losses by applying an estimated loss ratio to an estimate of ultimate earned premium for each underwriting year. The estimated loss ratio may be based on pricing information and/or industry data and/or historical claims experience revalued to the year under review;

•Bornhuetter-Ferguson method: The Bornhuetter-Ferguson method uses as a starting point an assumed IELR and blends in the claims experience to date using historical or benchmark loss development patterns on paid claims data or reported claims data. Although the method tends to provide less volatile indications at early stages of development and reflects changes in the external environment, it can be slow to react to emerging loss development and may, if the IELR proves to be inaccurate, produce loss estimates which take longer to converge with the final settlement value of loss; and

•Loss development method: The loss development method uses actual loss data and the historical development profiles on older underwriting years to project more recent, less developed years to their ultimate position.

Our actuaries may use other approaches in addition to those described, and supplement these methods with judgement where they deem appropriate, depending upon the characteristics of the class of business and available data.

For certain significant events, such as natural catastrophes or large man-made catastrophic events, traditional actuarial methods may not be suitable for estimating losses for reasons that may include lack of claims data or the existence of additional risks related to the specific event circumstances. For example, the estimates of loss reserves related to hurricanes and earthquakes can be affected by factors including, but not limited to, the inability to access portions of impacted areas, infrastructure disruptions, the complexity of the loss scenario, legal and regulatory uncertainties, complexities involved in estimating business interruption losses and additional living expenses, the impact of demand surge, fraud, and the limitations on available information. For hurricanes, additional complex coverage factors may include determining whether damage was caused by flooding or wind, evaluating general liability and pollution exposures and mold damage. Other recent examples include possible claims arising from the COVID-19 pandemic and the Ukraine conflict, where additional risks included material uncertainties around whether insured loss events had occurred, the timing of such events, and uncertainty over how contract wording applies in the case of insurance and reinsurance policies.

The timing of events can also affect the level of information available to the Company to estimate loss reserves for that reporting period, and therefore the reserving methods adopted. For example, for events occurring near the end of a reporting period, greater reliance may be placed on information derived from catastrophe models, and, where available and relevant, additional quantitative and qualitative exposure analyses, reports and communications of ground up losses from ceding companies, and development patterns for historically similar events. Due to the inherent uncertainty in estimating losses from such events, these estimates are subject to variability, which increases with the severity and complexity of the underlying event.

In addition to the Company’s quarterly reserving process, an independent actuarial review is carried out semi-annually by a leading independent actuarial consulting firm in order to provide additional insight into the reserving process, specific industry trends and the overall level of the Company’s loss reserves. Management reviews the information provided in the independent actuarial review in determining its own best estimate of reserves.

Management believes that it is prudent in its reserving assumptions and methodologies. However, we cannot be certain that our ultimate loss payments will not vary, perhaps materially, from the initial estimates made. We note that the process of estimating required reserves, by its very nature, involves uncertainty and therefore the ultimate claims may fall outside the actuarial range. The level of uncertainty can be influenced by many factors, including but not limited to unknown future in-claim value inflation, the existence of coverage with long duration reporting patterns, changes in the speed of claims data being received and processed, contractual uncertainties for unusual claim events, as well as the other factors previously discussed.

If we determine that adjustments to an earlier estimate are appropriate, such adjustments are recorded in the reporting period in which they are identified and may have a significant favorable or unfavorable impact on that period’s results of operations. We regularly review and update these estimates using the most current information available.

Management’s Best Estimate

The Company’s recorded reserves at each reporting date reflect management’s best estimate of the ultimate reserve for losses and loss adjustment expenses at that date. Management completes quarterly reserve studies for each exposure group for its International and Bermuda segments. Management analyzes significant variances between internal and external actuarial estimates, as well as any relevant additional market, underwriting or claims data that may be available and relevant for setting management’s best estimate of ultimate reserves. As a result of these considerations, the selected reserve estimate may be higher or lower than the indicated external actuarial estimate.

The Company’s best estimates are point estimates within a range of reasonable actuarial estimates. To provide an indication of the possible size of this range, in the following table we have compared the point estimate for net losses and loss adjustment expenses recorded by each reportable segment with a range of reasonable actuarial estimates:

It is important to note that the "High" and "Low" estimates above are not intended to be "worst-case" or "best-case" scenarios, and it is possible that final settlements of the reserves for these losses and loss adjustment expenses could fall outside of these ranges.

It is not appropriate to add together the ranges of each reportable segment in an effort to determine a high and low range around the Company’s total reserve for losses and loss adjustment expenses.

Prior Year Reserve Development

Prior year reserve development arises from changes to estimates for losses and loss adjustment expenses related to loss events that occurred in previous periods. Favorable prior year reserve development indicates that current estimates are lower than previous estimates, while unfavorable prior year reserve development indicates that current estimates are higher than previous estimates. The following table presents net prior year reserve development by reportable segment:

For a detailed discussion of net (favorable) unfavorable prior year reserve development by reportable segment for the years ended December 31, 2025, 2024 and 2023 see Results of Operations.

Claim Tail Analysis

One of the key selection characteristics for loss exposure groupings is the historical duration of the claims settlement process. Business in which claims are reported and settled relatively quickly are commonly referred to as short-tail lines, for example, property classes. On the other hand, business in which claims tend to take longer to be reported and settled are commonly referred to as long-tail lines, for example, casualty classes.

Although estimates of ultimate losses for short-tail business are usually inherently more certain than for medium and long-tail business, significant judgment is still required. Additionally, the inherent uncertainties relating to catastrophe events add further complexity to potential exposure estimation. Further, the Company uses MGAs and other producers for certain business, which can delay the receipt of loss information.

Although the Company uses similar actuarial methodologies for both short-tail and long-tail lines in respect of non-headline loss events, the faster reporting of experience for the short-tail lines allows management to have greater confidence in its estimates of ultimate losses for short-tail lines at an earlier stage than for long-tail lines. As a result, the Company’s estimates of ultimate losses for shorter tail lines, with the exception of loss estimates for headline loss events, generally exhibit less volatility than those for the longer tail lines. For longer tail lines, management utilizes exposure-based methods to estimate the Company’s ultimate losses, especially for immature years. For both short and long-tail lines, management supplements these general approaches with analytically based judgments.

Sensitivity Analysis

While management believes that the reserve for losses and loss adjustment expenses at December 31, 2025 is adequate, new information, events or circumstances may result in ultimate losses that are materially greater or less than initially recorded.

The tables below summarize, by reportable segment, the effect of reasonably likely scenarios on the key actuarial assumptions used to estimate the Company’s reserve for losses and loss adjustment expenses at December 31, 2025. The scenarios shown in the tables illustrate the effect of:

•changes to the expected loss ratio selections used at December 31, 2025, which represent loss ratio point increases or decreases to the expected loss ratios used. A higher expected loss ratio results in a higher ultimate loss estimate, and vice versa; and

•changes to the loss development patterns used in the Company’s reserving process at December 31, 2025, which represent claims reporting that is either slower or faster than the reporting patterns used. Accelerating a loss reporting pattern (i.e. shortening the claim tail) results in lower ultimate losses, as the estimated proportion of losses already incurred would be higher, and vice versa.

Management believes that the illustrated sensitivities are indicative of the materiality of these key actuarial assumptions to management’s best estimate of losses and loss adjustment expense reserves. The degree of stress applied to the expected loss ratio and loss development patterns were selected to be illustrative, and should not be considered to be "best case" or "worst case" for these assumptions. As such, it is important to recognize that future variations may be more or less than the amounts shown in the following table.

The effect of reasonably likely changes in the two key assumptions used to estimate the gross reserve for losses and loss adjustment expenses was as follows:

The results show the cumulative increase (decrease) in loss reserves across all years. Each of the impacts set forth is estimated individually, without consideration for any correlation among key assumptions or among reserve classes. Therefore, it would be inappropriate to take each of the amounts and add them together in an attempt to estimate total volatility. Additionally, it is noted that in some instances, for example, the projection of catastrophe estimates, development patterns are not appropriate as more bespoke techniques are used.