South Carolina · reference

South Carolina calendar and forms

Every South Carolina date that matters for the 2026 return, from the last estimated payment in January 2027 to the extended due date in October, and a plain-English guide to the forms and schedules an ordinary South Carolina filer will meet. Where to file free, how to check a refund, and how to reach the Department of Revenue.

By Charles Trautman, EA, editor

Need to Know Tax · written from South Carolina Department of Revenue (SCDOR) sources, November 3, 2026; updated November 12, 2026 after the election · not yet reviewed by a South Carolina practitioner

South Carolina keeps its calendar locked to the federal one. The SC1040 is due April 15, 2027, the same day as the federal return; the four estimated payments fall on the federal dates; and an extension runs six months to October 15, 2027. Two things are different from the federal routine. The extension is not automatic unless you owe nothing, so a filer with a balance either files Form SC4868 or makes a payment on MyDORWAY, which submits the extension by itself. And the threshold for estimated payments is low: the South Carolina Department of Revenue requires them when the expected tax after withholding is $100 or more.

The form side is short. There is one return, the SC1040, and a handful of schedules that attach only when they apply. For 2026 the SC1040 is being redesigned to start from federal adjusted gross income and to carry the new South Carolina Income Adjusted Deduction; the Department had not posted the 2026 form when this was written.

The 2027 filing season, dated

South Carolina dates for the 2026 return and 2027 payments
Date	What happens	Form
Thursday, October 15, 2026	The 2025 SC1040 is due under the automatic extension the Department granted every filer in March 2026; it is figured under the old law.	SC1040 (2025)
Friday, January 15, 2027	Fourth and final 2026 estimated payment due. Skip it if the 2026 return is filed and paid in full by February 1, 2027. Farmers and fishermen may make their single payment today.	SC1040ES
Late January 2027; the IRS announces the date in January	The Department begins accepting 2026 returns when the IRS opens. For the 2026 season refund time ran from February 2; the 2027 date is to come.	SC1040
Monday, March 1, 2027	Farmers and commercial fishermen who made no estimated payment must file and pay in full.	SC1040
Thursday, April 15, 2027	SC1040 and all 2026 tax due. Extension request or payment due. First 2027 estimated payment due. Last day a Future Scholar contribution counts for 2026.	SC1040, SC4868, SC1040ES
Tuesday, June 15, 2027	Second 2027 estimated payment due.	SC1040ES
Wednesday, September 15, 2027	Third 2027 estimated payment due.	SC1040ES
Friday, October 15, 2027	Extended due date for the 2026 SC1040.	SC1040
Tuesday, January 18, 2028	Fourth 2027 estimated payment due; January 15 is a Saturday and the 17th a holiday.	SC1040ES
Monday, April 15, 2030	Last day to claim a refund on the 2026 return: three years after the due date, by the same rule the 2025 instructions give as April 15, 2029 for the 2025 return.	SC1040, amended
February 15, 2027 is also the date to watch for the rate: the Board of Economic Advisors’ forecast in effect that day decides whether the 5.21% top rate falls for tax year 2027. Property tax bills run on the county’s calendar, not the Department’s; the homestead exemption is applied for once at the county auditor and does not appear on the SC1040.

How the extension works

A South Carolina extension is six months, to October 15, 2027, and it extends the time to file, not the time to pay. There are three ways to get it. If you owe no South Carolina tax, a federal Form 4868 is enough; the Department accepts a copy. If you owe, pay the balance on MyDORWAY at dor.sc.gov/pay, choosing Individual Income Tax Payment; the payment submits the extension and no form is needed. Or mail Form SC4868 with a check. Whichever way, the tax is due April 15. If less than 90% of the total tax is paid by then, a penalty of 0.5% a month runs on the shortfall, plus interest at the federal rate. Anyone who owes $15,000 or more on a return must file and pay electronically.

Estimated payments

South Carolina requires estimated payments from anyone who expects to owe $100 or more after withholding. The payments are due April 15, June 15, September 15 and January 15, and the safe harbor is the familiar one: 100% of last year’s tax in four equal, timely installments, 110% if last year’s AGI was over $150,000, or 90% of this year’s tax. Farmers and commercial fishermen with two-thirds of gross income from farming or fishing may pay once by January 15 or file and pay by March 1. The penalty is figured on Form SC2210.

Two 2026 cautions. The worksheet on the 2026 SC1040ES still shows the old 0%, 3% and 6% schedule, because the form went to print before Act 110; the Department’s September 2026 notice told payers to read Information Letter 26-20 before figuring the later installments. And the 2026 withholding tables, issued November 6, 2025, likewise predate the law. The people most often caught short are the self-employed, anyone with a large capital gain or Roth conversion, and in 2026 anyone who used to itemize.

The forms, in the order a filer meets them

South Carolina individual income tax forms, tax year 2026
Form	What it does	Who needs it
SC1040	The return. For 2026 it starts from federal AGI, subtracts the SCIAD, the dependent exemption and the state subtractions, applies the 1.99% and 5.21% rates, then credits, withholding and payments. An amended return is a new SC1040 with the Amended Return box checked and Schedule AMD attached; there is no separate amended form.	Everyone who files in South Carolina
SC1040TT	The tax table and rate schedule. The 2026 edition, to come, will carry the two new brackets.	Anyone figuring the tax by hand
Schedule NR	Nonresident and part-year resident schedule. Splits income into South Carolina and other columns and, from 2026, prorates the SCIAD and dependent exemption. Attached to the SC1040, never filed alone.	Anyone who moved in or out during 2026, or a nonresident with South Carolina income
SC1040TC	Nonrefundable credits not on the face of the return: tax paid to another state, nursing facility and in-home care, and others.	Residents taxed by another state; anyone with a specialized credit
I-335	Elects the flat 3% rate on active trade or business income from a sole proprietorship, partnership or S corporation.	Business owners for whom 3% beats 5.21%
I-319	Tuition tax credit: 50% of tuition at a South Carolina college, up to $1,500 a year, refundable.	Students and parents meeting the 30-credit-hour and other tests
SC1040ES	Estimated tax worksheet and four vouchers. Pay on MyDORWAY instead and skip the paper.	Anyone expecting to owe $100 or more after withholding
SC4868	Extension request. Needed only when tax is due and you are not paying on MyDORWAY.	Anyone filing after April 15 with a balance
SC1040V	Payment voucher for a balance due mailed separately from the return.	Paper payers; MyDORWAY replaces it
SC2210	Underpayment of estimated tax penalty, with the annualized income method and farmer and waiver codes.	Anyone who missed or shorted an installment
SC W-4	Employee withholding certificate given to the employer; not filed with the return.	Wage earners, especially in 2027 once tables reflect Act 110
Also: I-330 for voluntary check-off contributions, and I-435 for the pass-through entity election, which the business files, not the owner. All forms are on the Department’s forms page, reached from dor.sc.gov. The 2026 SC1040, SC1040TT and instructions are expected in December 2026 (verify).

Filing free

The Department does not run its own filing program; SC Fillable Forms ended in 2022. For the 2026 season it listed five Free File partners whose offers include a free South Carolina return: 1040.com (AGI $18,100 to $89,000), 1040NOW (AGI $32,000 or less, South Carolina residents), FreeTaxUSA and OLT.com (AGI $51,000 or less) and TaxSlayer (AGI $19,000 to $89,000, age 67 or younger, or EITC-eligible), most with a separate rule for active-duty military at $89,000 or less. The 2027 list is to come. The one rule that matters: start from the link on the Department’s Free Online Filing Options page. A vendor reached any other way may charge for the state return even when the federal return is free. South Carolina was not an IRS Direct File state.

Paying, and checking a refund

MyDORWAY, at dor.sc.gov/pay, takes estimated payments, extension payments, balances due and payment plan requests, and lists the payments already credited to you. The Department’s stated timeline for an error-free e-filed refund is up to eight weeks from February 2 or the filing date, whichever is later, most of it a fraud check of up to five weeks; amended returns take at least twelve weeks. Where’s My Refund needs your Social Security number and the exact refund amount, updates nightly, and the Department asks that you not call unless the status has not moved in more than eight weeks. Some filers get a letter directing them to MyDORWAY for an Identity Verification Quiz; the refund waits until it is done.

Reaching the Department
Purpose	Where
Individual income tax questions	1-844-898-8542; IITax@dor.sc.gov
Pay, check payments, verify identity, payment plans	MyDORWAY, dor.sc.gov/pay
Refund status	Where’s My Refund, from dor.sc.gov/Refund
Paper return with a refund or no balance	SC1040 Processing Center, PO Box 101100, Columbia, SC 29211-0100
Paper return with a balance due	Taxable Processing Center, PO Box 101105, Columbia, SC 29211-0105
SC1040ES, SC4868 or SC1040V with payment	SCDOR, IIT Voucher, PO Box 100123, Columbia, SC 29202
Correspondence	SC Department of Revenue, Income Tax, PO Box 125, Columbia, SC 29214-0400

Worked example: owing in April without the return finished

A self-employed filer expects to owe about $3,000 of South Carolina tax for 2026 but will not have the books closed by April 15, 2027, and files October 1. Two paths.

	Pays $3,000 on MyDORWAY April 15	Files SC4868, pays $2,000
Extension granted?	Yes, automatically with the payment	Yes
Paid by April 15 as a share of the $3,000 tax	100%	67%, under the 90% test
Extension penalty, 0.5% a month on the shortfall, 6 months	$0	$30 on $1,000
Interest at the federal rate from April 15	None	On $1,000

The second column is the common mistake: an extension with a guess that comes in under 90%. The penalty is small, but it is avoidable by paying a little more than you think you owe; the excess comes back as a refund or rolls into 2027 estimates. Paying nothing is worse: with tax due, a federal extension alone does not extend the South Carolina return, so late-filing penalties join the late-payment penalty.

Behind the scenes: why 2025 returns are due in October 2026

In March 2026 the Department granted every South Carolina filer an automatic extension of the 2025 return to October 15, 2026, while Act 110 was moving through the legislature and Information Letter 26-4 was settling the add-backs for the 2025 federal law. The result is an unusual overlap: 2025 returns under the old law were still being filed in the autumn of 2026, while the 2026 withholding tables and estimated vouchers in use all year were printed for a law that no longer exists. The 2027 season is the first under the new return, and the Department has said the 2026 forms, a SCIAD calculator on MyDORWAY and revised withholding tables are coming.

What to bring

Every W-2 and 1099 with South Carolina withholding
The 2026 estimated payments made, with dates and amounts; MyDORWAY lists them
Last year’s SC1040, for the 100% or 110% safe harbor
If you moved or paid tax to another state: the move date, income by period, and the other state’s return
Any letter from the Department, especially an identity verification notice

Questions people ask

Is the South Carolina extension automatic?

Only if you owe nothing; then a federal extension covers you. If you owe, make a payment on MyDORWAY by April 15, which files the extension for you, or mail Form SC4868 with a check. Either way the tax is due April 15, and the extension runs to October 15.

Do I have to make estimated payments?

If you expect to owe $100 or more after withholding, yes. Paying 100% of last year’s tax in four equal installments avoids any penalty, 110% if last year’s AGI was over $150,000. Retirees with a large Roth conversion and the self-employed are the usual people who miss this.

How do I amend a South Carolina return?

File a new SC1040 for that year with the Amended Return box checked and Schedule AMD attached. There is no separate amended form. Refund claims generally run three years from the original due date.

How long will my refund take?

The Department says up to eight weeks for an error-free e-filed return, counted from February 2 or the filing date, whichever is later, and at least twelve weeks for an amended return. Check Where’s My Refund rather than calling; the representatives see the same screen.

Will the 2026 SC1040 look like last year’s?

No. It starts from federal AGI instead of federal taxable income and adds a line for the South Carolina Income Adjusted Deduction; the old lines tied to federal taxable income go away. Expect the form and its instructions in December 2026.

Federal dates, a $100 estimated-payment trigger, and an extension that comes with the payment

Pay by April 15 even if the return comes in October, keep the four estimated dates, and start any free-file return from the Department’s own page.

Written by Charles Trautman, EA, editor  ·  Need to Know Tax, Lone Tree, Colorado
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Forms and official pages named in this article

Sources and where to check

Updated November 12, 2026, after the November 3 election · tax year 2026 figures · awaiting review by a South Carolina practitioner — use the right article