State Conformity
Tax Glossary Term
Definition
State conformity is the degree to which a state's income tax code adopts (conforms to) the federal Internal Revenue Code. Most states start their income tax calculation from federal adjusted gross income or federal taxable income, meaning they automatically inherit federal deductions and exclusions unless they explicitly decouple. Conformity comes in three main forms: rolling conformity (the state automatically adopts all federal changes as they happen), fixed-date conformity (the state adopts the IRC as of a specific date and must pass new legislation to update), and selective conformity (the state picks and chooses which federal provisions to adopt). This concept became especially important with the One Big Beautiful Bill Act (OBBBA), because states that do not conform to the new IRC Sections 224 and 225 may still tax tips and overtime income that is federally deductible. Some states have already announced they will decouple from one or more OBBBA deductions; others have passed conformity bills. Taxpayers in non-conforming states may owe state tax on income they excluded federally, creating an addback on the state return. When evaluating a state's tax burden, checking its conformity status is essential — a state with a low rate but no OBBBA conformity could cost a tipped worker more than a higher-rate state that fully conforms.
Example
A server in State X earns $20,000 in tips during the year.
Federally, she deducts $20,000 under the OBBBA tips deduction on Schedule 1-A.
State X has fixed-date conformity to the IRC as of January 1, 2024, before the OBBBA was enacted.
Result: State X does not recognize the tips deduction.
Her state taxable income is $20,000 higher than her federal taxable income.
She must add back the $20,000 on her state return.