South Carolina generally conforms to federal tax law and uses federal taxable income as the starting point for state tax calculations. However, provisions within the "One, Big, Beautiful, Bill Act," enacted federally in mid-2025, were finalized after the South Carolina legislative session had concluded. Consequently, these changes have not yet been incorporated into state law.
Until the legislature votes to conform to this Act, specific federal deductions are not recognized by the state and must be added back to your taxable income.
This currently impacts your return in two ways:
- Itemized Deductions: Certain deductions allowed on your federal return (such as the additional SALT deduction) are currently disallowed under South Carolina law and must be added back.
- Standard Deduction: The increased standard deduction amounts passed in OBBBA must also be added back (that is the $750 you see when you switch to standard deduction.)
Taxpayers claiming deductions for overtime, tips, and the additional deduction for taxpayers over age 65 will also see add-backs for these amounts.
A comprehensive list of affected items can be found in this recent SC Information Letter.
It is currently unknown if or when the legislature will address conformity. Given this uncertainty, you have two options:
- File your federal return now and wait to file your South Carolina return until more information is available.
- File both returns now. Please be aware that if the state legislature passes conformity retroactively, you may need to file an amended state return.
While there is a possibility that the South Carolina Department of Revenue (DOR) could automatically adjust returns filed prior to conformity, the timing and mechanics of such a resolution are currently unknown.
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