# EDGAR Filing Document

**Accession Number:** 0000874501
**File Stem:** 0001628280-25-057024
**Filing Date:** 2025-12
**Character Count:** 13748
**Document Hash:** dc40703fdaa489cf5990470d753fc652
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001628280-25-057024.hdr.sgml**: 20251215

**ACCESSION NUMBER**: 0001628280-25-057024

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 17

**CONFORMED PERIOD OF REPORT**: 20251210

**ITEM INFORMATION**: Changes in Registrant's Certifying Accountant

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20251215

**DATE AS OF CHANGE**: 20251215

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** OCTAVE SPECIALTY GROUP INC
- **CENTRAL INDEX KEY:** 0000874501
- **STANDARD INDUSTRIAL CLASSIFICATION:** SURETY INSURANCE [6351]
- **ORGANIZATION NAME:** 02 Finance
- **EIN:** 133621676
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-10777
- **FILM NUMBER:** 251571854

**BUSINESS ADDRESS:**
- **STREET 1:** ONE WORLD TRADE CENTER
- **STREET 2:** ONE WORLD TRADE CENTER
- **CITY:** NEW YORK
- **STATE:** NY
- **BUSINESS PHONE:** 2126587470

**MAIL ADDRESS:**
- **STREET 1:** ONE WORLD TRADE CENTER
- **STREET 2:** ONE WORLD TRADE CENTER
- **CITY:** NEW YORK
- **STATE:** NY

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** AMBAC FINANCIAL GROUP INC
- **DATE OF NAME CHANGE:** 19980121

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** AMBAC INC /DE/
- **DATE OF NAME CHANGE:** 19930328

?xml version='1.0' encoding='ASCII'? ambc-20251210

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION** 

**Washington, D.C. 20549** 

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| | |
|:---|:---|
| **FORM** | **8-K** |

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**CURRENT REPORT**

**PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934**

**Date of Report (Date of earliest event reported): December 10, 2025**

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| |
|:---|
| Octave Specialty Group, Inc. |
| **(Exact name of Registrant as specified in its charter)** |

---

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| | | |
|:---|:---|:---|
| **Delaware** | **1-10777** | **13-3621676** |
| **(State of incorporation)** | **(Commission<br>file number)** | **(I.R.S. employer<br>identification no.)** |

---

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| | | | |
|:---|:---|:---|:---|
| **40 Wall Street** | **New York** | **NY** | **10005** |
| **(Address of principal executive offices)** | **(Address of principal executive offices)** | **(Address of principal executive offices)** | **(Address of principal executive offices)** |

---

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| | |
|:---|:---|
| **(212)** | **658-7470** |
| **(Registrant's telephone number, including area code)** | **(Registrant's telephone number, including area code)** |

---

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| | | | |
|:---|:---|:---|:---|
| **Ambac Financial Group, Inc.** | **Ambac Financial Group, Inc.** | **Ambac Financial Group, Inc.** | **Ambac Financial Group, Inc.** |
| **Former Name** | **Former Name** | **Former Name** | **Former Name** |
| **One World Trade Center** | **New York** | **NY** | **10007** |
| **Former Address** | **Former Address** | **Former Address** | **Former Address** |

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Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4c))

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| | | |
|:---|:---|:---|
| Securities registered pursuant to Section 12(b) of the Act: | Securities registered pursuant to Section 12(b) of the Act: | Securities registered pursuant to Section 12(b) of the Act: |
| **Title of each class** | **Trading Symbol** | **Name of each exchange on which registered** |
| Common stock, par value $0.01 per share | OSG | New York Stock Exchange |

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Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 under the Securities Act (17 CFR 230.405) or Rule 12b-2 under the Exchange Act (17 CFR 240.12b-2).

Emerging growth company ☐

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| | |
|:---|:---|
| If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to | If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to |
| Section 13(a) of the Exchange Act. | ☐ |

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**Item 4.01 Change in Registrant's Certifying Accountant** 

*(a) Dismissal of Previous Independent Registered Public Accounting Firm* 

As a matter of good corporate governance, the Audit Committee of the Board of Directors (the "Audit Committee") of Octave Specialty Group, Inc., formerly known as Ambac Financial Group, Inc., (the "Company") has been taking a number of steps in consideration of a potential audit firm rotation. Of particular consideration is that recent acquisitions have resulted in the Company having multiple audit firms. KPMG LLP ("KPMG"), the Company's current independent registered public accounting firm, has served as the Company's auditor since 1985. Therefore, the Company and Audit Committee invited several independent registered public accounting firms, including KPMG, to respond to an audit services request for proposal ("RFP").

On December 10, 2025, the Company completed a competitive RFP process to determine the Company's independent registered public accounting firm for the fiscal year ending December 31, 2026. Following an extensive evaluation process and with the approval of the Audit Committee, the Company chose not to continue with the engagement of KPMG. The Company notified KPMG on December 10, 2025, that it will be dismissed as the Company's independent registered public accounting firm, upon completion of their audits of the Company's consolidated financial statements as of and for the year ended December 31, 2025, and the effectiveness of internal control over financial reporting as of December 31, 2025, and the issuance of their reports thereon. The audit reports of KPMG on the Ambac Financial Group, Inc. and subsidiaries' consolidated financial statements as of and for the years ended December 31, 2024 and 2023, did not contain an adverse opinion or a disclaimer of opinion, and were not qualified or modified as to uncertainty, audit scope, or accounting principles. The audit reports of KPMG on the effectiveness of internal control over financial reporting as of December 31, 2024 and 2023, did not contain any adverse opinion or disclaimer of opinion, nor were they qualified or modified as to uncertainty, audit scope, or accounting principles. During the Company's two most recent fiscal years ended December 31, 2024, and 2023, and the subsequent interim period through December 10, 2025, there were no disagreements, within the meaning of Item 304(a)(1)(iv) of Regulation S-K promulgated under the Exchange Act ("Regulation S-K") and the related instructions thereto, with KPMG on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which disagreements, if not resolved to the satisfaction of KPMG, would have caused them to make reference to the subject matter of the disagreements in connection with their reports. Also during this same period, there were no reportable events within the meaning of Item 304(a)(1)(v) of Regulation S-K and the related instructions thereto. The Company has provided KPMG with the disclosures under this Item 4.01(a), and requested KPMG to furnish the Company with a letter addressed to the Securities and Exchange Commission stating whether KPMG agrees with the statements made by the Company in this Item 4.01(a). KPMG's letter is filed as Exhibit 16.1 to this Current Report on Form 8-K.

*(b) Appointment of New Independent Registered Public Accounting Firm* 

On December 10, 2025, the Audit Committee approved the appointment of Ernst and Young LLP ("EY") as the Company's new independent registered public accounting firm, subject to completion of EY's client acceptance procedures and execution of engagement agreement(s), for the audit of the Company's financial statements for the year ended December 31, 2026. During the Company's two most recent fiscal years ended December 31, 2024 and 2023, and the subsequent interim periods through December 15, 2025, neither the Company nor anyone acting on its behalf consulted with EY regarding any of the matters described in Items 304(a)(2)(i) and (ii) of Regulation S-K.

**Item 9.01. Financial Statements and Exhibits**

(d) Exhibits. The following exhibits are filed as part of this Current Report on Form 8-K

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**EXHIBIT INDEX**

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| | |
|:---|:---|
| **Exhibit<br>Number** | **Exhibit Description** |
| 16.1 | <u>[Letter from KPMG LLC dated December 15, 2025](a04-0914q20258xkex161.htm)</u> |
| 99.1 | <u>[Press Release dated December 15, 2025](a04-0914q20258xkex991.htm)</u> |
| 101.INS | XBRL Instance Document - the instance document does not appear in the interactive Data File because its XBRL tags are embedded within the Inline XBRL document. |
| 101.SCH | XBRL Taxonomy Extension Schema Document. |
| 101.CAL | XBRL Taxonomy Extension Calculation Linkbase Document. |
| 101.LAB | XBRL Taxonomy Extension Label Linkbase Document. |
| 101.PRE | XBRL Taxonomy Extension Presentation Linkbase Document. |
| 101.DEF | XBRL Taxonomy Extension Definition Linkbase Document. |
| 104 | Cover Page Interactive Data File - The cover page interactive data file does not appear in the Interactive Data File because its XBRL tags or embedded within the Inline XBRL document |

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**SIGNATURES** 

**Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.** 

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| | | | |
|:---|:---|:---|:---|
| | | **Ambac Financial Group, Inc.** | **Ambac Financial Group, Inc.** |
| | | **(Registrant)** | **(Registrant)** |
| **Dated:** | **December 15, 2025** | **By:** | **/s/ William J. White** |
|  |  |  | **William J. White** |
|  |  |  | **First Vice President, Secretary and<br>Assistant General Counsel** |

---

## Exhibit 16.1

**Exhibit 16.1**

![kpmglogo.jpg](kpmglogo.jpg)

KPMG LLP

Two Manhattan West

375 9th Avenue, 17th Floor

New York, NY 10001

December 15, 2025

Securities and Exchange Commission<br>Washington, D.C. 20549

Ladies and Gentlemen:

We are currently principal accountants for Octave Specialty Group, Inc., formerly known as Ambac Financial Group, Inc., (the "Company") and, under the date of March 6, 2025, we reported on the consolidated financial statements of Ambac Financial Group, Inc. and subsidiaries' as of and for the years ended December 31, 2024 and 2023, and the effectiveness of internal control over financial reporting as of December 31, 2024. On December 10, 2025, we were notified that the Company selected Ernst and Young LLP as its principal accountant for the year ending December 31, 2026 and that the auditor-client relationship with KPMG LLP will cease upon completion of the audit of the Company's consolidated financial statements as of and for the year ended December 31, 2025, and the effectiveness of internal control over financial reporting as of <br>December 31, 2025, and the issuance of our reports thereon. We have read the Company's statements included under Item 4.01 of its Form 8-K dated December 15, 2025, and we agree with such statements, except that we are not in a position to agree or disagree with the Company's stated reason for changing principal accountants, the Company's statement related to a competitive and extensive selection process, or the Company's statements in Item 4.01(b).

Very truly yours,

![kpmgsignature.jpg](kpmgsignature.jpg)

## Exhibit 99.1

**Exhibit 99.1**

**Octave Specialty Announces Auditor Change**

Audit Committee Appoints Ernst & Young LLP as Auditor for the Year Ended December 31, 2026

KPMG to Remain the Auditor for the Year Ended December 31, 2025

New York, NY December 15, 2025 (Business Wire) – Octave Specialty Group, Inc. (NYSE:OSG) today announced that as a result of a review process, the Audit Committee of its Board of Directors has approved the engagement of Ernst & Young LLP ("EY") as the Company's independent registered public accounting firm for the Company's fiscal year ended December 31, 2026, subject to completion of EY's client acceptance procedures and the execution of an engagement letter. KPMG LLP ("KPMG"), the Company's current independent registered public accounting firm, will continue as the Company's independent registered public accounting until the filing of the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2025. The review process was not related to any disagreement between the Company and KPMG.

**About Octave**

Octave Specialty Group, Inc. is a global specialty insurance firm that builds, buys, and scales niche insurance distribution and underwriting businesses. With a focus on operational excellence, disciplined growth, and innovation, Octave is creating a harmonized portfolio of companies that deliver exceptional performance and long-term value for shareholders. For more information, visit <u>www.octavegroup.com</u>.

Investors:

Karen Beyer<br>Managing Director, Investor Relations<br><u>kbeyer@octavegroup.com</u>

Media:<br>Kate Smith<br>Director, Corporate Communications<br><u>ksmith@octavegroup.com</u>

<br>