White Mountains Insurance Group, Ltd. filed a Form 8-K on November 5, 2026, announcing its results for the three and nine months ended September 30, 2026, along with detailed disclosures of 14 non-GAAP financial measures used in the accompanying press release.

Key Highlights

  • Reporting period: Results cover the three and nine months ended September 30, 2026, as disclosed in the press release attached as Exhibit 99.1.
  • Ark's tangible book value: According to the filing, Ark's tangible book value was $1,824.6 million as of September 30, 2026, compared with $1,736.4 million as of June 30, 2026, and $1,673.6 million as of December 31, 2025.
  • Ark's year-to-date tangible book value growth: The filing reports year-to-date growth in tangible book value, including dividends, of 12.0% as of September 30, 2026.
  • Ark's GAAP book value: Ark's GAAP book value was reported at $1,673.2 million as of September 30, 2026, up from $1,593.9 million at December 31, 2025.
  • 14 non-GAAP measures disclosed: The filing identifies 14 non-GAAP financial measures covering Ark, Kudu, Distinguished, and WTM Partners, all stated to be reconciled from their most comparable GAAP measures.
  • Year-to-date dividends declared: Ark's year-to-date dividends declared were $50.5 million as of September 30, 2026, according to the filing.

White Mountains Discloses Q3 2026 Financials and Non-GAAP Reconciliations

White Mountains Insurance Group, Ltd. (NYSE:WTM), a Bermuda-incorporated holding company headquartered in Hanover, New Hampshire, furnished a Form 8-K on November 5, 2026, under Item 2.02 (Results of Operations and Financial Condition). The filing attaches a press release as Exhibit 99.1 covering the company's performance for the three and nine months ended September 30, 2026.

The filing discloses 14 non-GAAP financial measures, covering four business units: Ark, Kudu, Distinguished, and WTM Partners. For Ark, the filing defines tangible book value as GAAP book value adjusted to exclude goodwill and other intangible assets, offset by a deferred tax liability on those intangibles, and further adjusted for a contingent consideration liability. The contingent consideration liability, according to the filing, "represents the estimated fair value of the additional shares that could be earned by management rollover shareholders if and to the extent that White Mountains achieves certain multiple of invested capital return thresholds." The filing states that if earned, these additional shares "would result in a reallocation of economics among Ark's shareholders" but "would have no impact on Ark's stand-alone book value or tangible book value."

For Kudu, the filing describes EBITDA, adjusted EBITDA, annualized adjusted EBITDA, annualized revenue, and cash revenue yield as non-GAAP measures, each reconciled from GAAP net income (loss) or net investment income. Adjustments to Kudu's EBITDA include net realized and unrealized investment gains or losses on participation contracts, non-cash equity-based compensation, and transaction expenses. For Distinguished, the filing introduces ScaleCo measures that exclude the results of the GrowthCo vertical, which the filing notes "is consolidated under GAAP." White Mountains states it "believes that these non-GAAP financial measures are useful to management and investors in evaluating" the underlying performance of each respective business unit.

What Was Disclosed

White Mountains Insurance Group filed an 8-K on November 5, 2026, furnishing a press release with Q3 and nine-month 2026 results, including Ark's tangible book value of $1,824.6 million at September 30, 2026, and definitions and reconciliations for 14 non-GAAP financial measures across its business units.