White Mountains officer reports tax withholding of company shares

White Mountains Insurance Group executive MD & Chief Accounting Officer reported a routine change in holdings.

Rhea-AI Filing Summary

White Mountains Insurance Group executive MD & Chief Accounting Officer reported a routine change in holdings. On January 1, 2026, 600 restricted common shares became unrestricted, and 274 common shares were withheld by the company to cover the reporting person's tax obligations. This withholding is shown as a disposition transaction.

After this event, the reporting person beneficially owned 2,491 common shares and 1,225 restricted common shares directly, plus 20 common shares held indirectly through a 401(k) plan.

Insider Trade Summary

Exercise Price or Tax Liability: 274 shares

Exercise Price or Tax Liability 3 txns

Insider Hildreth Michaela

Role MD & Chief Accounting Officer

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Common Shares	274	$2,078.03	$569K
holding	Common Shares (Restricted)	--	--	--
holding	Common Shares	--	--	--

Holdings After Transaction: Common Shares — 2,491 shares (Direct); Common Shares (Restricted) — 1,225 shares (Direct); Common Shares — 20 shares (Indirect, by 401(k))

Footnotes (1)

1. F1. On January 1, 2026, 600 restricted Common Shares became unrestricted. 274 of the Common Shares were withheld by the Company to satisfy the Reporting Person's tax obligations.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did White Mountains (WTM) report here?

The MD & Chief Accounting Officer reported that on January 1, 2026, 274 common shares of White Mountains Insurance Group were withheld by the company to satisfy tax obligations when restricted shares became unrestricted.

Why were 274 White Mountains (WTM) shares withheld from the insider?

The filing states that out of 600 restricted common shares that became unrestricted on January 1, 2026, 274 shares were withheld by White Mountains Insurance Group to satisfy the reporting person's tax obligations.

How many White Mountains (WTM) shares does the insider own after this transaction?

Following the reported transaction, the insider beneficially owns 2,491 common shares and 1,225 restricted common shares directly, and 20 common shares indirectly through a 401(k) plan.

What is the insiders role at White Mountains (WTM)?

The reporting person is an officer of White Mountains Insurance Group, serving as MD & Chief Accounting Officer.

Is this White Mountains (WTM) insider transaction a sale on the open market?

No. The filing explains that the 274 common shares were withheld by the company to cover tax obligations when restricted shares vested, which is different from an open-market sale.

Does the insider hold any White Mountains (WTM) shares indirectly?

Yes. The insider holds 20 common shares indirectly through a 401(k) plan, in addition to their directly held common and restricted shares.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 01/05/2026 - 09:09 AM Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Hildreth Michaela

(Last) (First) (Middle)

C/O WHITE MOUNTAINS INSURANCE GROUP, LTD

23 SOUTH MAIN STREET, SUITE 3B

(Street)

HANOVER NH 03755

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
WHITE MOUNTAINS INSURANCE GROUP LTD [ WTM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	MD & Chief Accounting Officer

3. Date of Earliest Transaction (Month/Day/Year)
01/01/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Shares	01/01/2026		F		274	D	$2,078.03	2,491(1)	D
Common Shares (Restricted)								1,225(1)	D
Common Shares								20	I	by 401(k)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. On January 1, 2026, 600 restricted Common Shares became unrestricted. 274 of the Common Shares were withheld by the Company to satisfy the Reporting Person's tax obligations.

	Wesley C Bell, by Power of Attorney	01/02/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.