WTM White Moutains Insurance Group Ltd

QuickLinks -- Click here to rapidly navigate through this document

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

---

SCHEDULE TO

Tender Offer Statement under Section 14(d)(1) or 13(e)(1)
of the Securities Exchange Act of 1934

---

WHITE MOUNTAINS INSURANCE GROUP, LTD.
(Name of Subject Company (Issuer) and Filing Person (Issuer and Offeror))

---

Common Shares, par value $1.00 per share
(Title of Class of Securities)

---

G9618E107
(CUSIP Number of Class of Securities)

---

Robert L. Seelig, Esq.
Executive Vice President and General Counsel
White Mountains Insurance Group, Ltd.
80 South Main Street
Hanover, New Hampshire 03755-2053
Telephone: (603) 640-2200
(Name, address and telephone number of person authorized to receive notices and communications on behalf of filing persons)

---

With a copy to:
Ting S. Chen, Esq.
Cravath, Swaine & Moore LLP
825 Eighth Avenue
New York, New York 10019
Telephone: (212) 474-1000

---

CALCULATION OF FILING FEE:

o

Check the box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

o

Check the box if the filing relates solely to preliminary communications made before the commencement of the tender offer.

          Check the appropriate boxes below to designate any transactions to which the statement relates:

o

third-party tender offer subject to Rule 14d-1.



ý

issuer tender offer subject to Rule 13e-4.



o

going-private transaction subject to Rule 13e-3.



o

amendment to Schedule 13D under Rule 13d-2.

          Check the following box if the filing is a final amendment reporting the results of the tender offer:     o

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

o

Rule 13e-4(i) (Cross-Border Issuer Tender Offer)



o

Rule 14d-1(d) (Cross-Border Third-Party Tender Offer)

   

---

INTRODUCTION

        This Issuer Tender Offer Statement on Schedule TO (" Schedule TO ") relates to the tender offer by White Mountains Insurance Group, Ltd., a company organized under the laws of Bermuda (the " Company "), to purchase 500,000 of its issued and outstanding Common Shares, par value $1.00 per share (the " Common Shares " or the " Shares "), or such lesser number of Shares as is properly tendered and not properly withdrawn, at a price not greater than $875 or less than $825 per Share, net to the seller in cash, less any applicable withholding taxes and without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase dated April 10, 2018 (the " Offer to Purchase "), a copy of which is attached hereto as Exhibit (a)(1)(A), and in the related Letter of Transmittal (the " Letter of Transmittal " and, together with the Offer to Purchase, as they may be amended or supplemented from time to time, the " Offer "), a copy of which is attached hereto as Exhibit (a)(1)(B), which are herein incorporated by reference. This Schedule TO is being filed in accordance with Rule 13e-4 under the Securities Exchange Act of 1934, as amended (the " Exchange Act ").

        All information in the Offer is hereby expressly incorporated by reference in answer to all items in this Schedule TO, and as more particularly set forth below.

Item 1.    Summary Term Sheet.

        The information set forth in the Offer to Purchase under "Summary Term Sheet" is incorporated herein by reference.

Item 2.    Subject Company Information.

        (a)   The name of the issuer is White Mountains Insurance Group, Ltd., a company organized under the laws of Bermuda. The Company's principal executive offices are located at 80 South Main Street, Hanover, New Hampshire 03755-2053, telephone: (603) 640-2200.

        (b)   The class of securities to which this statement relates is the Common Shares, par value $1.00 per share, of which 3,753,405 Shares were issued and outstanding as of April 9, 2018.

        (c)   The information set forth in the Offer to Purchase under Section 7 ("Price Range of Shares; Dividends") is incorporated herein by reference.

Item 3.    Identity and Background of Filing Person.

        (a)   This Tender Offer Statement on Schedule TO is filed by the Company, which is also the issuer. The Company's address and telephone number are set forth under Item 2. The information set forth in the Offer to Purchase under Schedule I and Section 11 ("Interests of Directors and Executive Officers; Transactions and Arrangements Concerning the Shares") is incorporated herein by reference.

Item 4.    Terms of the Transaction.

        (a)   The following information set forth in the Offer to Purchase is incorporated herein by reference:

•

"Summary Term Sheet";



•

"Introduction";



•

Section 1 ("Number of Shares; Proration");



•

Section 2 ("Procedures for Tendering Shares");



•

Section 3 ("Withdrawal Rights");



•

Section 4 ("Acceptance for Payment and Payment for Shares");

2

---

•

Section 5 ("Purpose of the Offer; Certain Effects of the Offer");



•

Section 6 ("Certain U.S. Federal Income Tax Consequences");



•

Section 8 ("Conditions to the Offer");



•

Section 11 ("Interest of Directors and Executive Officers; Transactions and Arrangements Concerning the Shares"); and



•

Section 14 ("Extension of the Offer; Termination; Amendment").

        (b)   The information set forth in the Offer to Purchase under "Summary Term Sheet", "Introduction", Section 5 ("Purpose of the Offer; Certain Effects of the Offer") and Section 11 ("Interest of Directors and Executive Officers; Transactions and Arrangements Concerning the Shares") is incorporated herein by reference.

Item 5.    Past Contacts, Transactions, Negotiations and Agreements.

        (e)   The information set forth in the Offer to Purchase under Section 11 ("Interests of Directors and Executive Officers; Transactions and Arrangements Concerning the Shares") is incorporated herein by reference.

Item 6.    Purpose of the Transaction and Plans or Proposals.

        (a)   The information set forth in the Offer to Purchase under "Summary Term Sheet" and Section 5 ("Purpose of the Offer; Certain Effects of the Offer") is incorporated herein by reference.

        (b)   The information set forth in the Offer to Purchase under Section 5 ("Purpose of the Offer; Certain Effects of the Offer") is incorporated herein by reference.

        (c)   The information set forth in the Offer to Purchase under "Summary Term Sheet", "Introduction", Section 5 ("Purpose of the Offer; Certain Effects of the Offer"), Section 9 ("Certain Information Concerning the Company") and Section 10 ("Source and Amount of Funds") is incorporated herein by reference.

Item 7.    Source and Amount of Funds or Other Consideration.

        (a), (b) and (d) The information set forth in the Offer to Purchase under "Summary Term Sheet" and Section 10 ("Source and Amount of Funds") is incorporated herein by reference.

Item 8.    Interest in Securities of the Subject Company.

        (a)   and (b) The information set forth in the Offer to Purchase under Schedule I and Section 11 ("Interests of Directors and Executive Officers; Transactions and Arrangements Concerning the Shares") is incorporated herein by reference.

Item 9.    Persons/Assets Retained, Employed, Compensated or Used.

        (a)   The information set forth in the Offer to Purchase under "Introduction" and Section 15 ("Fees and Expenses") is incorporated herein by reference.

Item 10.    Financial Statements.

        Not applicable.

3

---

Item 11.    Additional Information.

        (a)(1)  The information set forth in the Offer to Purchase under Section 11 ("Interests of Directors and Executive Officers; Transactions and Arrangements Concerning the Shares") is incorporated herein by reference.

        (a)(2)  The information set forth in the Offer to Purchase under Section 12 ("Certain Legal Matters") is incorporated herein by reference.

        (a)(3)  Not applicable.

        (a)(4)  The information set forth in the Offer to Purchase under Section 13 ("Effects of the Offer on the Market for Shares; Registration Under the Exchange Act") is incorporated herein by reference.

        (a)(5)  None.

        (b)   The information set forth in the Offer to Purchase and the Letter of Transmittal, as each may be amended or supplemented from time to time, is incorporated herein by reference.

Item 12.    Exhibits.

4

---

Item 13.    Information Required by Schedule 13E-3.

        Not applicable.

5

---

INDEX OF EXHIBITS

6

---

SIGNATURE

        After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

7

---

QuickLinks

INTRODUCTION

Item 1. Summary Term Sheet.
Item 2. Subject Company Information.
Item 3. Identity and Background of Filing Person.
Item 4. Terms of the Transaction.
Item 5. Past Contacts, Transactions, Negotiations and Agreements.
Item 6. Purpose of the Transaction and Plans or Proposals.
Item 7. Source and Amount of Funds or Other Consideration.
Item 8. Interest in Securities of the Subject Company.
Item 9. Persons/Assets Retained, Employed, Compensated or Used.
Item 10. Financial Statements.
Item 11. Additional Information.
Item 12. Exhibits.
Item 13. Information Required by Schedule 13E-3.

INDEX OF EXHIBITS
SIGNATURE