UNITIL CORP Income Taxes Disclosure

Note 9: Income Taxes

In December 2023, the FASB issued ASU 2023-09 – Income taxes: Improvements to Income Tax Disclosures which includes amendments that further enhance income tax disclosures and income taxes paid by jurisdiction. The Company has

elected to adopt ASU 2023-09 on a prospective basis. The following table presents the Company’s provisions for Income Taxes and the provisions calculated at the statutory federal tax rate for the year ended December 31, 2025:

Under the Company’s Tax Sharing Agreement (the Agreement) which was approved upon the formation of Unitil as a public utility holding company, the Company files consolidated Federal and State tax returns and Unitil Corporation and each of its utility operating subsidiaries recognize the results of their operations in its tax returns as if it were a stand-alone taxpayer. The Agreement provides that the Company will account for income taxes in compliance with U.S. GAAP and regulatory accounting principles. The Company has evaluated its tax positions at December 31, 2025 in accordance with the FASB Codification, and has concluded that no adjustment for recognition, de-recognition, settlement or foreseeable future events to any tax liabilities or assets as defined by the FASB Codification is required.

In August 2025, Unitil Corporation received notice that its Federal Income Tax return filing for the year ending December 31, 2023 is under examination by the IRS. Currently, the Company believes that the ultimate resolution of this examination will not have a material impact on the Company’s financial statements. The Company remains subject to examination by Federal, Maine, Massachusetts, and New Hampshire tax authorities for the tax periods ended December 31, 2024; December 31, 2023; and December 31, 2022.

Income tax filings for the year ended December 31, 2024 have been filed with the IRS, Massachusetts Department of Revenue, the Maine Revenue Service, and the New Hampshire Department of Revenue Administration. In the Company’s federal tax returns for the year ended December 31, 2024 which were filed with the IRS in October 2025, the Company utilized federal Net Operating Loss Carryforward (NOLC) assets of $5.6 million and $1.0 million of federal tax credit carryforward. As of December 31, 2025, the Company has fully utilized all NOLC and federal tax credits available. In addition, at December 31, 2025, the Company had $1.8 million of cumulative state tax credit carryforwards to offset future income taxes payable. If unused, the Company’s state tax credit carryforwards will begin to expire in 2027.

On July 4, 2025, the One Big Beautiful Bill Act (OBBBA) was enacted into law. The OBBBA provided permanent and limited modifications to many provisions that had expired or would soon expire as well as eliminating many green energy provisions. The Company does not expect that the OBBBA will have a material effect on the Company's Consolidated Financial Statements.

On April 14, 2023, the IRS issued Revenue Procedure 2023-15 that provides a safe harbor method of accounting that taxpayers may use to determine whether to deduct or capitalize expenditures to repair, maintain, replace, or improve natural gas transmission and distribution property. Under the revenue procedure, the method of accounting will depend on the property’s classification as linear transmission property, linear distribution property, or non-linear property. The revenue procedure may be adopted in tax years ending after May 1, 2023. The Company elected a change in its tax accounting method on the 2023 consolidated tax return. A 481(a) adjustment was calculated and resulted in an additional $9.4 million in tax expense on the 2023 consolidated tax return.

In December 2017, the Tax Cuts and Jobs Act (TCJA), which included a reduction of the corporate federal income tax rate to 21% effective January 1, 2018, was signed into law. In accordance with FASB Codification Topic 740, the Company revalued its Accumulated Deferred Income Taxes (ADIT) and recorded a net liability in the amount of $48.9 million at December 31, 2017. The Company expects to flow through to customers $47.1 million of excess ADIT in utility base rates. The benefit of protected excess ADIT amounts will be subject to flow back to customers in utility rates according to the Average Rate Assumption Method (ARAM). The Company estimates the ARAM flow back period for protected and unprotected excess ADIT to be between fifteen and twenty years over the remaining life of the related utility plant. As of December 31, 2025, the Company flowed back $13.9 million to customers in its Massachusetts, Maine, New Hampshire and federal jurisdictions.