1099 Quarterly Taxes in South Carolina (2025-2026)
If you're self-employed in South Carolina — freelancer, contractor, gig worker, or single-member LLC — you owe quarterly estimated taxes to two agencies: the IRS (federal) and South Carolina Department of Revenue (state). South Carolina's top marginal rate is 6.4%, applied progressively. Getting your estimates right matters because under-payment penalties stack on top of the actual tax owed.
South Carolina state income tax (2025)
South Carolina uses a progressive bracket system on top of federal tax. For single filers in 2025:
| Income (single filer) | Marginal rate |
|---|---|
| $0 – $3,460 | 0.00% |
| $3,460 – $17,330 | 3.00% |
| $17,330+ | 6.40% |
How to pay South Carolina estimated taxes
Federal estimated tax due dates (April 15, June 16, 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.
South Carolina-specific quirk freelancers miss
South Carolina has been steadily lowering its top rate from 7% in 2022 to 6.4% in 2025, with further planned reductions toward 6%. The 0% bracket on the first $3,460 of taxable income provides modest relief for low-income filers.
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.
- SEP-IRA / Solo 401(k) contributions reduce both federal and South Carolina taxable income.
- Self-employed health insurance premiums are deductible federally.