Unitil Corporation (UTL) details Corporate Secretary transition and consulting role

Rhea-AI Filing Summary

Unitil Corporation reported an upcoming leadership transition in its corporate governance team. Corporate Secretary Sandra L. Whitney has given notice that she will retire and resign from the company and its subsidiaries effective at the end of the day on December 31, 2025.

As part of its succession plan, Unitil will appoint Carleton B. Simpson, currently Senior Vice President and General Counsel, as Corporate Secretary effective January 1, 2026. He will continue serving as General Counsel while taking on the additional Corporate Secretary role. The company expects Ms. Whitney to provide consulting services through April 30, 2026 to support a smooth transition of responsibilities.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

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 15, 2025

UNITIL CORPORATION

(Exact name of registrant as specified in its charter)

New Hampshire		1-8858		02-0381573
(State or other jurisdiction		(Commission		(IRS Employer
of incorporation)		File Number)		Identification No.)

6 Liberty Lane West, Hampton, New Hampshire		03842-1720
(Address of principal executive offices)		(Zip Code)

Registrant’s telephone number, including area code: (603) 772-0775

N/A

(Former name or former address, if changed since last report)

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-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol		Name of each exchange of which registered
Common Stock, no par value		UTL		New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

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. ☐

Item 7.01 Regulation FD Disclosure

On December 15, 2025, Sandra L. Whitney, Corporate Secretary of Unitil Corporation (the “Company”), provided notice that she will retire and, in connection with her retirement, resign from the Company and each of its subsidiaries, effective as of the end of the day on December 31, 2025.

As part of the Company’s ongoing succession plan, the Company will appoint Carleton B. Simpson as Corporate Secretary of the Company, effective as of January 1, 2026. Mr. Simpson is currently Senior Vice President and General Counsel of the Company. He will continue in that role in addition to becoming the Corporate Secretary of the Company.

The Company anticipates that Ms. Whitney will provide consulting services to the Company until April 30, 2026, to help with the transition of duties.

Item 8.01 Other Events

The first two paragraphs of Item 7.01 are incorporated by reference into this Item 8.01.

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.

UNITIL CORPORATION
By:		/s/ Daniel J. Hurstak
		Name: Daniel J. Hurstak
		Title: Senior Vice President, Chief Financial Officer and Treasurer

Date: December 18, 2025