Income tax
South Carolina state income tax (2026)
South Carolina uses a progressive bracket system on top of federal tax. For single filers in 2026:
| Income (single filer) | Marginal rate |
|---|---|
| $0 – $30,000 | 1.99% |
| $30,000+ | 5.21% |
South Carolina · 1099 quarterly taxes · 2026
1099 Quarterly Taxes in South Carolina (2026)
If you earn 1099 income in South Carolina, your quarterly tax bill splits across two agencies: the IRS for federal, and South Carolina Department of Revenue for state. South Carolina's top marginal rate is 5.21%, applied progressively. Underpayment penalties stack on the actual tax owed, so the safe-harbor math matters.
How to pay
How to pay South Carolina estimated taxes
Federal estimated tax due dates (April 15, June 15, September 15, 2026, and January 15, 2027) apply to your South Carolina state estimated payments as well — most states piggyback on the federal schedule. Pay South Carolina taxes through the South Carolina Department of Revenue's online portal: mydorway.dor.sc.gov. You can also mail Form SC1040ES with a check.
Penalties
South Carolina safe harbor and underpayment penalty
Federal and state estimated tax safe harbors work in parallel for South Carolina freelancers. Hit the federal safe harbor (90% of current-year federal tax OR 100% of prior-year federal tax — 110% if your prior-year AGI exceeded $150,000) and you avoid the IRS underpayment penalty on Form 2210.
For South Carolina state estimated taxes, most filers can match the federal safe harbor approach by paying 100% of last year's South Carolina tax in four equal quarterly installments. South Carolina's underpayment penalty is calculated on the state's equivalent of Form 2210 — the SCDOR can assess interest plus a flat penalty on the under-paid amount.
Practical advice for South Carolina self-employed taxpayers: pay both federal and state estimates on the same quarterly schedule (April 15, June 15, September 15, January 15). File your federal payment via IRS Direct Pay and your state payment via South Carolina MyDORWAY. Keep records of every payment — both agencies can request proof if the safe-harbor math is challenged later.
Estimated tax
Paying South Carolina estimated taxes — what to know
Four operational details unique to South Carolina that catch new self-employed taxpayers:
- Use Form SC1040ES. Form SC1040ES is South Carolina's estimated tax voucher for self-employed individuals. You can file via SCDOR's online portal (South Carolina MyDORWAY) for free direct-debit payments, or mail a check with the paper voucher. Online payments confirm in real time; paper vouchers post after 7-10 business days.
- South Carolina's top marginal rate is 5.21%. Plan your quarterly estimates by applying your effective South Carolina rate (usually lower than 5.21% for most freelancers, but higher than zero) on top of your federal tax. The state portion typically lands between 2% and 7% of net SE income depending on bracket position.
- State return starts from federal AGI. Most South Carolina freelancers don't realize that the state return uses federal AGI as the starting point, then applies state-specific modifications. Get your federal Schedule C right first — every error there flows downstream to your South Carolina return.
- South Carolina contact: South Carolina Department of Revenue. If you have a specific question about your state estimated taxes — payment confirmations, address corrections, refund tracking — go directly to SCDOR via their online portal.
South Carolina-specific quir
South Carolina-specific quirk freelancers miss
South Carolina restructured its income tax for TY 2026 via H.4216 (signed March 2026): a two-tier structure with 1.99% on income under $30,000 and 5.21% above (minus a $966 credit). This replaced the previous 6.4% top rate that had been on a glide path toward 6%.
Common filing mistakes
Common filing mistakes South Carolina freelancers make
Five recurring mistakes the South Carolina DOR sees from self-employed filers:
- Paying federal estimates but skipping state. The federal safe harbor doesn't protect you from a South Carolina state underpayment penalty. Both calendars need to be paid on the same quarterly schedule.
- Forgetting the 15.3% SE tax. SE tax (12.4% Social Security + 2.9% Medicare on 92.35% of net SE earnings) is in addition to federal income tax AND South Carolina state tax. New freelancers consistently miss this 15.3% layer when budgeting.
- Using gross income instead of net for estimates. Both federal and South Carolina tax apply to your net SE income after deductions, not your gross receipts. Skipping legitimate business expenses inflates your estimate by 20-40%.
- Missing the South Carolina-specific quirk. South Carolina restructured for TY 2026 via H.4216 — 1.99% on first k, 5.21% above, minus a credit. This catches first-year filers because federal-tax software often doesn't surface state-specific quirks.
- Not tracking conformity differences. SC conforms to federal QBI deduction. Misalignments between federal and state taxable income are the most common source of surprise state tax bills.
Deductions
Common deductions for South Carolina freelancers
- South Carolina allows the same business expenses (home office, mileage, software, etc.) as federal.
- Half of SE tax is deductible federally; check South Carolina's rules for state conformity.
- SC conforms to federal QBI deduction.
- Self-employed health insurance premiums are deductible federally.