South Carolina follows the federal calendar across entity types. For the 2025 tax year, individual and C-corporation returns are due April 15, 2026, and S-corporation and partnership returns are due March 16, 2026. The state offers an entity-level rate election that pairs with a corporate license fee, and it withholds on nonresident owners by default. Those are the details that shape a South Carolina business engagement.

What are South Carolina's 2026 tax filing deadlines?

For the 2025 tax year, the South Carolina individual return (SC1040) and C-corporation return (SC1120) are due April 15, 2026. The S-corporation return (SC1120S) and partnership return (SC1065) are due March 16, 2026, since the statutory March 15 date, the 15th day of the third month, falls on a Sunday.

How does South Carolina's extension work?

Individuals get an automatic six-month extension to October 15, 2026 with Form SC4868, and paying through MyDORWAY submits the extension automatically. Partnerships and fiduciaries use Form SC8736 instead. The extension is to file only; you must pay at least 90% of the tax by April 15, 2026 to avoid penalty.

What is South Carolina's I-435 entity-level election?

South Carolina lets a partnership or S-corporation elect to have its active trade or business income taxed at the entity level at a flat 3% rather than passing through to the owners. The election is annual, made on Form I-435 attached to the SC1065 or SC1120S, with owners reconciling on Form I-335. It is a rate election on active business income, so model the entity-level 3% against the owners' individual rates before electing.

What is the South Carolina corporate license fee?

A C-corporation owes an annual license fee in addition to the 5% corporate income tax. The fee is 0.1% of capital and paid-in surplus plus $15, with a $25 minimum. It applies every year, so a South Carolina corporation has a small fixed cost on top of its income tax even in a thin year.

How does South Carolina tax nonresident pass-through owners?

The entity withholds. A pass-through must withhold 5% of the South Carolina income allocable to nonresident owners, remitted with the entity return, unless the owner files an I-309 affidavit consenting to South Carolina jurisdiction. The entity can also file a composite return covering its nonresident owners.

Who owes South Carolina estimated tax?

Individuals expecting to owe $100 or more file a declaration and pay quarterly on April 15, June 15, September 15, 2026, and January 15, 2027 (Form SC1040ES). Corporations expecting to owe $100 or more in tax after credits make quarterly payments as well.

How does a firm handle South Carolina at scale?

South Carolina's dates are conventional, so the attention goes to the elections and the fixed fee. The I-435 active-business election is a yearly modeling decision, the license fee applies to every C-corporation regardless of income, and the 5% nonresident withholding is the default unless the owner files the affidavit. Track which entities elected I-435 and which owners filed an I-309, and the South Carolina book runs clean. See how we think about scaling tax prep workflows.

Where do these dates come from?

All deadlines and thresholds here trace to the South Carolina Department of Revenue. Verify against the source before filing.