On March 5, 2026, Ohio Governor Mike DeWine signed into law Senate Bill 9 (SB 9), which updates Ohio's Internal Revenue Code (IRC) conformity.

SB 9 updates Ohio Rev. Code 5701.11, the state's IRC conformity provision, to the effective date of the legislation — March 5, 2026 — and incorporates recent changes to the IRC taking effect after March 7, 2025 (from March 15, 2023). The incorporated changes include those made by the "One Big Beautiful Bill Act" (OBBBA). The most significant OBBBA provisions affecting Ohio law include allowing a deduction for domestic research and experimental expenses, increasing the cap on deductible business interest and allowing 100% depreciation of the adjusted basis of qualified production property in the year in which property is placed into service.

SB 9 also permits taxpayers with a tax year ending after 7 March 2025 and before 5 March 2026, to irrevocably elect to incorporate all IRC provisions that were effective in their 2025 tax year (2026 tax year for some fiscal-year taxpayers). Taxpayers would make the election on their 2025 tax return (2026 tax return for some fiscal-year taxpayers). The election allows Ohio taxpayers to incorporate the changes made by the OBBBA into their latest return. Similar elections made under prior versions of Ohio Rev. Code 5701.11 remain in effect for the tax years to which those elections applied.

SB 9 takes immediate effect.

Implications

Taxpayers should be aware of the changes and consider how the updated IRC conformity may impact their tax liabilities and reporting requirements for the upcoming tax year.