South Carolina quarterly estimated tax payments are due April 15, June 15, September 15, and January 15 of the following year, and you owe them if you expect your state income tax after withholding and credits to reach $100 or more for the year.1South Carolina Legislature. South Carolina Code 12-6-3910 – Estimated Tax Payments Form; Due Dates; Treatment of Excess Where Estimated Payments or Withholdings More Than Tax Liability; Waiver of Penalties2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax You calculate the amount on the SC1040ES worksheet, split it into four equal installments, and pay online through MyDORWAY or by mailing a paper voucher.
Who Has to Pay
The $100 threshold is the state’s own figure, lower than the federal $1,000 under IRC Section 6654.1South Carolina Legislature. South Carolina Code 12-6-3910 – Estimated Tax Payments Form; Due Dates; Treatment of Excess Where Estimated Payments or Withholdings More Than Tax Liability; Waiver of Penalties It catches most people who earn income the state can’t reach through automatic withholding: freelancers and independent contractors, landlords, investors with dividend or capital gains income, and retirees whose pension withholding isn’t enough to cover their South Carolina liability. Full-year and part-year residents are both covered if their income exceeds the minimum filing threshold.
The Four Deadlines
Calendar-year taxpayers owe payments on:1South Carolina Legislature. South Carolina Code 12-6-3910 – Estimated Tax Payments Form; Due Dates; Treatment of Excess Where Estimated Payments or Withholdings More Than Tax Liability; Waiver of Penalties
- April 15 (first quarter)
- June 15 (second quarter)
- September 15 (third quarter)
- January 15 of the following year (fourth quarter)
When a deadline falls on a weekend or state-recognized holiday, it rolls to the next business day. Timeliness is judged by the postmark on a mailed payment or the electronic timestamp on an online one. Fiscal-year filers substitute the months matching the 4th, 6th, 9th, and 13th months of their fiscal year.1South Carolina Legislature. South Carolina Code 12-6-3910 – Estimated Tax Payments Form; Due Dates; Treatment of Excess Where Estimated Payments or Withholdings More Than Tax Liability; Waiver of Penalties
Calculating What You Owe Each Quarter
The SC1040ES form on the SCDOR website contains a worksheet that walks through the calculation. Project your South Carolina taxable income for the year, apply the current rate, subtract credits and withholding, and if the result is $100 or more, divide by four.2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax Most people start from last year’s SC1040 and adjust for changes they expect.
For 2026 the rate is a flat 3.99%, replacing the graduated brackets used in prior years.3South Carolina Department of Revenue. Information About H. 4216 The math is simpler, but any rule of thumb built on the old brackets needs to be thrown out and redone.
Safe Harbor
You avoid the underpayment penalty entirely if your withholding plus estimated payments equal at least the lesser of 90% of the current year’s tax or 100% of the prior year’s tax. If your prior-year adjusted gross income exceeded $150,000 ($75,000 if married filing separately), the second figure rises to 110% of that year’s tax.4Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax Hitting the safe harbor is a clean pass regardless of what your actual current-year tax turns out to be.
How to Pay
Online Through MyDORWAY
MyDORWAY is the SCDOR’s free portal and the fastest way to pay. It accepts checking and savings accounts as well as Visa, Mastercard, American Express, and Discover credit cards, with no convenience fees.2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax You can schedule all four installments in advance.5South Carolina Department of Revenue. MyDORWAY If you pay online, don’t also mail a paper voucher for the same quarter.
By Mail
To pay by check, use the paper vouchers packaged with the SC1040ES. Make the check payable to SCDOR and write your name, Social Security number, and “2026 SC1040ES” in the memo line. Mail the voucher and check to:2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax
SCDOR, IIT Voucher
PO Box 100123
Columbia, SC 29202
Use a separate voucher for each quarter, write in black ink, and don’t send cash. If you owe $15,000 or more on any SCDOR return, state law requires you to file and pay electronically.2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax
When Your Income Changes Mid-Year
If your income, dependents, or withholding shift enough that your estimated tax “substantially increased or decreased,” the SCDOR expects you to file an adjusted declaration by the next payment due date.2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax Page 4 of the SC1040ES has an Adjusted Declaration Schedule for the recalculation. You rerun the numbers with your corrected figures and spread the remaining balance over the quarters still to come. A big freelance contract in August or a property sale in October is exactly the kind of event this schedule is built for.
What Happens If You Underpay
The SCDOR calculates the penalty using simple interest on each quarter’s shortfall: underpayment × days overdue ÷ 365 × the applicable rate.6South Carolina Department of Revenue. SC2210 – Underpayment of Estimated Tax by Individuals, Estates, and Trusts For 2026 the rate is 7% through March 31 and 6% starting April 1.7South Carolina Department of Revenue. SC Information Letter 26-9 You don’t have to run the numbers; the SCDOR will bill you. Part III of Form SC2210 is the worksheet if you want to check the math yourself.
You’re exempt from the penalty if your current-year tax after refundable credits is under $100, or if your payments cleared a safe harbor.6South Carolina Department of Revenue. SC2210 – Underpayment of Estimated Tax by Individuals, Estates, and Trusts
Requesting a Waiver
The SCDOR can waive the penalty in full for reasonable cause, meaning you exercised ordinary business care and still couldn’t pay on time. A partial waiver is possible when reasonable cause is not fully present but mitigating factors weigh in your favor, taking your filing history and the nature of the error into account.8South Carolina Department of Revenue. Penalty Waiver A casualty, disaster, or other unusual circumstance where the penalty would be inequitable also qualifies.6South Carolina Department of Revenue. SC2210 – Underpayment of Estimated Tax by Individuals, Estates, and Trusts Any request has to come in as a signed, written explanation of the facts; the SCDOR won’t act on a waiver without one. Financial hardship on its own is not grounds for a waiver.
If Your Income Is Uneven or Seasonal
Two rules exist for taxpayers whose earnings don’t fit a four-equal-installments assumption. If at least two-thirds of your gross income in the current or prior year comes from farming or commercial fishing, you can make one payment by January 15 instead of four, or skip estimated payments entirely by filing and paying your SC1040 in full by March 1.2South Carolina Department of Revenue. SC1040ES – Individual Declaration of Estimated Tax
Everyone else with lumpy income can use the annualized income installment method, which bases each quarterly payment on what you actually earned in that period.6South Carolina Department of Revenue. SC2210 – Underpayment of Estimated Tax by Individuals, Estates, and Trusts It’s useful for seasonal businesses, real estate agents whose closings cluster in summer, and anyone taking a large one-time payment late in the year. You calculate using a Schedule AI adapted for South Carolina and file it with Form SC2210. The paperwork is heavier, but it can shrink or eliminate a penalty when the income truly wasn’t spread evenly.