How to File South Carolina Form SC1120-T: Payment, Submission, Penalties

South Carolina Form SC1120-T gives a corporation an automatic six-month extension to file its state income tax return, but only if the form (or an equivalent MyDORWAY payment) is submitted by the 15th day of the fourth month after the tax year ends, with full payment of both the estimated corporate income tax and the annual license fee.¹ For calendar-year filers, that date is April 15. The extension moves the filing deadline. It does not move the payment deadline.²

Who Files SC1120-T

C-corporations, S-corporations, and nonprofit entities with income subject to federal tax all use SC1120-T when they need more time to prepare the South Carolina return. S-corporations that normally file SC1120-S use the same SC1120-T; there is no separate S-corp extension form.¹ If your fiscal year does not match the calendar, adjust the deadline accordingly. A corporation with a June 30 year-end files its SC1120-T by October 15.

When You Can Skip the Form

If your corporation expects to owe no South Carolina tax for the year, you may not need to file SC1120-T at all. The Department of Revenue will accept a copy of a properly filed federal extension (typically Form 7004) in place of the state form, provided the final return reaches SCDOR within the time the IRS allows.¹ This shortcut only works when nothing is due. If you owe any income tax or license fee, you must file the SC1120-T with payment or pay through MyDORWAY by the original deadline.

What You Have to Pay With the Extension

SC1120-T is a payment vehicle, not just a time request. Two separate obligations must be satisfied by the original due date:

Your estimated South Carolina corporate income tax, computed at the 5% corporate rate.²
The annual corporate license fee, which is 0.1% of capital and paid-in surplus plus $15, with a $25 minimum. Every C-corporation and S-corporation owes it.²

The license fee is a common oversight. The form instructions explicitly require paying all of it alongside all income tax due before the extension is honored.¹

How to Submit It

Online Through MyDORWAY

MyDORWAY is the Department of Revenue’s free portal at MyDORWAY.dor.sc.gov.³ To register you need your FEIN or SSN, your SCDOR file number, and either a Letter ID or a copy of your last return.¹ Paying your extension amount through MyDORWAY automatically extends your filing time, so you do not need to send in a separate SC1120-T form. The portal issues immediate confirmation, which is your proof of a timely request.

By Mail

To file on paper, send the completed SC1120-T with a check or money order for the net amount due to:

SCDOR
Corporate Voucher
PO Box 100153
Columbia, SC 29202-1350¹

The envelope must be postmarked no later than the original due date. The state does not mail a confirmation for paper submissions, so watch for the payment to clear your bank.

Filling Out the Form

SC1120-T is a single page. At the top, enter your Federal Employer Identification Number, your SCDOR file number, and the date your tax year ends. If you cannot find your SCDOR file number, check a prior-year state return.

The financial section is a short calculation. Estimate your total South Carolina income tax at the 5% rate, subtract any quarterly estimated payments you already made and any overpayment carried forward from last year, subtract any tax credits you plan to claim, and send the remaining balance with the form. An authorized corporate officer must sign and date it. Download the current-year version from the SCDOR website; using an out-of-date form can cause processing problems.

Penalties and Interest If You Underpay or Miss It

The extension buys filing time, not payment relief. Several charges can apply, and they can stack:

If the amount paid with the extension is less than 90% of your actual tax for the year, an underpayment penalty applies to the shortfall from the original due date until paid.¹
Failing to pay the full amount shown on any return by the due date triggers a late-payment penalty of 0.5% of the unpaid tax per month, up to 25%.⁴
Skipping the extension and missing the filing deadline altogether triggers a failure-to-file penalty of 5% of the unpaid tax per month, capped at 25%.⁴

Interest runs on top. Under South Carolina law, tax is considered due on the last day prescribed for payment regardless of any extension, and interest accrues from that original due date at the federal underpayment rate set under IRC Section 6621(a)(2).⁵ A valid extension does not stop interest from accumulating on any unpaid balance.

Filing the Final Return

When your six-month window closes, file the full corporate return: SC1120 for C-corporations, SC1120-S for S-corporations. Mark the “Extension” box on the front of the return to tell SCDOR that a state or federal extension was in place.¹ Any tentative payment made with SC1120-T or through MyDORWAY is credited against your final liability. If you overpaid, request a refund or apply the excess to next year’s estimated tax. If you underpaid, send the difference with the return to stop additional penalties and interest from running.

1
South Carolina Department of Revenue. Application for Automatic Extension of Time to File Corporate Tax Return
2
South Carolina Department of Revenue. C Corporation
3
South Carolina Department of Revenue. MyDORWAY
4
South Carolina Legislature. South Carolina Code Title 12 Chapter 54 – Section 12-54-43
5
South Carolina Legislature. South Carolina Code Section 12-54-25 – Interest Due on Late Payments