Every material Form 8-K WHITE MOUNTAINS INSURANCE GROUP LTD has filed with the SEC since August 06, 2026, read and summarized by AI: what happened, the key figures, whether it reads positive or negative for shareholders, and how big a deal it is (impact 1-5). Newest first; each brief links to its own page and to the filing on SEC.gov.
White Mountains Insurance Group reported a net loss attributable to common shareholders of $39 million for the third quarter of 2026, compared with income of $114 million a year earlier, and book value per share fell 1% to $2,243 as of September 30, 2026. Unrealized investment losses, including a $54 million mark-to-market loss on its MediaAlpha stake after a 24% share price decline, drove the result, which matters to shareholders because the book value per share is the company's main measure of value.
Third-quarter 2026 net income (loss) attributable to common shareholders was $(39) million, versus $114 million in Q3 2025; first nine months were $133 million, versus $271 million.
Third-quarter total revenues were $641 million, down from $864 million in Q3 2025.
Book value per share was $2,243 at September 30, 2026, down 1% for the quarter and up 3% for the first nine months, including dividends.
On November 4, 2026, the company agreed to sell 5.5 million MediaAlpha shares at $13.90 per share, leaving it with 12.4 million shares.
White Mountains Insurance Group elected Stephen Klar, former President and Managing Partner of Wellington Management Group, as a director on August 26, 2026, raising the board from 10 to 11 members. The filing describes this as a routine board addition with standard non-employee director pay, and it discloses no financial results or transactions.
Board elected Stephen Klar as a director on August 26, 2026; board size increased from 10 to 11 persons
Klar was formerly President and a Managing Partner of Wellington Management Group LLP
Klar receives standard non-employee director compensation, including a pro-rated cash and common equity retainer for the rest of 2026
Filing states no arrangements with other persons and no material interest in related-party transactions
White Mountains reported second-quarter 2026 net income attributable to common shareholders of $199.5 million, or $80.58 per share, up from $122.9 million a year earlier. Book value per share rose 4.1% in the quarter, including dividends, to $2,257.60 as of June 30, 2026, and the company repurchased $191 million of its shares in the quarter.
Q2 2026 net income attributable to common shareholders was $199.5 million, compared with $122.9 million in Q2 2025; diluted EPS was $80.58 versus $47.75.
Six-month net income attributable to common shareholders was $172.3 million, compared with $156.8 million in the first six months of 2025.
Book value per share was $2,257.60 as of June 30, 2026, up 4.1% in the quarter including dividends.
In Q2 2026 the company repurchased and retired 91,194 shares for $191 million at an average price of $2,092.72.
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