South Carolina largely conforms to the federal filing calendar, and it has been steadily cutting its top individual rate. It offers a flat 3% elective tax on pass-through business income, and one timing note is material this cycle.
South Carolina Tax Deadlines at a Glance (2026)
Entity Type | Return Due | Extended Due Date |
|---|---|---|
Individuals (SC1040) | April 15, 2026 | October 15, 2026 |
C Corporations (SC1120) | April 15, 2026 | October 15, 2026 |
S Corporations (SC1120S) | March 16, 2026 | September 15, 2026 |
Partnerships (SC1065) | March 16, 2026 | September 15, 2026 |
South Carolina’s dates track the federal calendar: individuals and C corporations file by April 15, while S corporations and partnerships follow the third-month deadline of March 16, 2026 (March 15 is a Sunday), extending to September 15. Note this cycle: SCDOR administratively extended the 2025 individual filing deadline to October 15, 2026 pending federal conformity legislation — but any tax owed is still due by April 15.
Rates: Top Individual Rate Now 6.0%
South Carolina’s top individual income tax rate is 6.0% for the 2025 tax year — down from 6.2% in 2024 — on a graduated structure that starts at 0%. (Further reductions toward a lower flat rate are proposed but not yet effective for 2025 — do not apply a sub-6% rate.) The corporate income tax rate is 5.0%.
The Active Trade or Business PTE Tax
South Carolina offers an elective Active Trade or Business tax — a flat 3% entity-level tax on qualifying pass-through business income, elected via Form I-435 and reconciled by owners on Form I-335. In effect since 2021 and active for 2026, it is a long-standing SALT-planning tool for South Carolina business owners.
Estimates, Extensions, and Penalties
Individual estimated payments (SC1040ES) are due April 15, June 15, September 15, 2026, and January 15, 2027, required if expected liability is $100 or more. South Carolina accepts the federal extension. Interest ties to the federal underpayment rate (7% for early 2026), and an extension covers filing only, not payment.
CPA Action Steps
Apply the 6.0% top rate for 2025 (not 6.2%)
File SC1120S and SC1065 by March 16 (weekend roll)
Note the administrative extension of the 2025 individual filing deadline to October 15
Consider the flat 3% Active Trade or Business election
Verify current rates and dates against the South Carolina Department of Revenue (dor.sc.gov) before filing.