Car loan interest deduction in South Carolina
The car loan interest deduction is a federal benefit. What it means for your South Carolina return depends on whether South Carolina taxes income and how it follows the federal rules.
The federal car loan interest deduction (tax years 2025–2028) applies in South Carolina the same as anywhere — if your vehicle is new, personal-use, US-assembled, financed with a 2025–2028 loan, and your income is under the phase-out. Whether it also lowers your South Carolina state tax depends on state conformity — see below.
South Carolina income tax at a glance
- State income tax
- Graduated, up to 6%
- Return starts from federal AGI
- No — its own income base
- Conformity to federal changes
- Fixed-date — adopts the code as of a set date
- State tax agency
- South Carolina Department of Revenue
How state conformity works
Because the deduction is above-the-line, it reduces your federal adjusted gross income (AGI). Whether that also lowers your South Carolina taxable income depends on how South Carolina conforms to the federal tax code:
- Rolling conformity: the state automatically adopts federal changes as they happen, so a new above-the-line deduction like this one generally flows through to the state return.
- Static (fixed-date) conformity: the state only adopts the federal code as of a set date, so a brand-new 2025 provision does not flow through until the state updates that date — you may get the federal deduction but no state benefit.
South Carolina uses static (fixed-date) conformity — it adopts the federal code only as of a set date, not automatically. A brand-new 2025 federal provision like this one does not flow through to your South Carolina return until the state advances its conformity date, so you may get the federal deduction but no South Carolina benefit for now. Verify the latest position with the South Carolina Department of Revenue.
This reflects South Carolina's general conformity method, not a ruling on this specific deduction — always confirm the current year with the South Carolina Department of Revenue or a tax professional.
Your combined federal + South Carolina saving
The deduction is a deduction, not a credit — it saves you your marginal rate on the qualifying interest, not the interest itself. Federally that's your IRS bracket; in South Carolina, at a top rate of 6%, the deduction adds a state saving only if the state adopts this 2025 provision. Estimate both:
Confirm your federal eligibility first
State treatment only matters if you qualify federally. Check the three tests that trip people up: