South Carolina Estimated Tax Payments 2026: New Rates, SC1040ES Dates, and the $100 Rule

South Carolina estimated tax payments for 2026 are due in four equal installments: April 15, June 15, September 15, 2026, and January 15, 2027, paid on Form SC1040ES or through MyDORWAY. You must prepay once you expect to owe $100 or more after withholding, one of the lowest prepayment triggers of any state income tax. The bigger 2026 story is H. 4216: South Carolina scrapped its 0%/3%/6% schedule for two rates, 1.99% on the first $30,000 of taxable income and 5.21% above it, which means most 2026 bills come in below 2025's and the 90%-of-current-year safe harbor usually beats paying 100% of last year.

Key takeaways:

• Trigger: prepay through withholding or estimates if you'll owe $100+ on your SC1040 (Minnesota's line is $500, the federal line $1,000)
• Due dates: April 15, June 15, September 15, 2026, and January 15, 2027, at 25% each
• New 2026 rates under H. 4216: 1.99% up to $30,000 of taxable income, 5.21% above; the 0% bracket no longer exists
• New deduction: the South Carolina Income Adjusted Deduction of $15,000 single / $22,500 head of household / $30,000 joint, phasing out at higher incomes
• Safe harbor: the lesser of 90% of 2026 tax or 100% of 2025 tax (110% once prior-year AGI tops $150,000; $75,000 married filing separately)

Save this cheat sheet — the South Carolina numbers in one image.

When Are South Carolina Estimated Tax Payments Due in 2026?

South Carolina follows the federal quarterly calendar with four even installments, per the SC2210 payment schedule:

September 15 is a two-voucher day: federal Q3 on Form 1040-ES and the third SC1040ES. One built-in escape exists at year-end: file your 2026 SC1040 and pay the balance by January 31, 2027, and no penalty applies to the January 15 installment, while the meter on any earlier underpayments stops at January 15. Farmers and fishermen earning two-thirds of gross income from those activities can skip vouchers entirely by filing and paying by March 1, 2027.

Who Must Pay? South Carolina's $100 Rule

The SC2210 instructions state it in one line: if you owe an income tax liability of $100 or more on your SC1040, you must prepay it through withholding or estimated tax payments. There is no penalty when your total tax minus withholding stays under $100, and none when your 2025 liability was zero across a full 12-month year.

A $100 trigger reaches far down the income scale. At the new 1.99% bottom rate, about $5,000 of South Carolina taxable income with no withholding already creates a $100 liability. In practice that pulls in nearly every 1099 contractor, freelancer, landlord, and pass-through owner in the state; run your federal side through the 1099 tax calculator and remember South Carolina expects its slice quarterly too. W-2 employees are usually covered, because South Carolina counts withholding as paid evenly across all four installment dates.

See What the SCDOR Expects From You

H. 4216 Rewrote the 2026 Math: New Rates and the SCIAD

H. 4216, effective beginning with the 2026 tax year, replaced South Carolina's three-bracket schedule (0% to $3,560, 3% to $17,830, 6% above) with a two-rate structure:

The law also decoupled South Carolina from the federal standard deduction. In its place sits the South Carolina Income Adjusted Deduction (SCIAD): $15,000 for single filers, $22,500 for head of household, $30,000 for joint filers, phasing out as income rises (for singles, between roughly $40,000 and $95,000 of income) until high earners get none. Future cuts are wired in too: the top rate steps down automatically in years when state revenue projections grow 5% or more.

Worked example. Darnell, a self-employed electrician in Greenville (single), projects $52,000 of South Carolina taxable income for 2026 after his deductions, including a partially phased-out SCIAD. His 2026 tax: 1.99% on the first $30,000 ($597) plus 5.21% on the remaining $22,000 ($1,146) = $1,743. The shortcut formula agrees: 5.21% × $52,000 − $966 = $1,743.

Why 90% of 2026 Usually Beats the Prior-Year Safe Harbor This Year

South Carolina's required annual payment is the lesser of 90% of your 2026 tax or 100% of your 2025 tax, with the prior-year option rising to 110% once 2025 adjusted gross income exceeds $150,000 ($75,000 married filing separately). In a normal year the prior-year anchor wins for anyone whose income is growing, because it is a known number. 2026 is not a normal year: the rate cut pushed most bills down, so 90% of the new, smaller liability is frequently the cheaper harbor.

Darnell's 2025 South Carolina tax was $2,510 under the old 0%/3%/6% schedule. His options: 100% × $2,510, or 90% × $1,743 = $1,569. Choosing the current-year route sets each SC1040ES payment at $392 and keeps about $941 of the year in his pocket versus autopiloting last year's number. The trade-off is real, though: the 90% test measures his actual 2026 tax. If a busy fourth quarter pushes taxable income past his estimate, the SC2210 penalty applies per installment, while the $2,510 anchor would have been bulletproof. Underestimating on purpose is how the cheap harbor becomes the expensive one.

How to Pay: MyDORWAY or SC1040ES by Mail

MyDORWAY, the SCDOR's free portal at dor.sc.gov/pay, takes estimated payments without an account: select Individual Income Tax Payment, enter your SSN or ITIN and legal name, choose Estimated Payment, and pay by ACH debit or card with no convenience fee. You get instant confirmation, and the SC1040ES instructions are explicit: do not mail a paper voucher for a quarter you paid online.

By mail, send the 2026 SC1040ES voucher with the correct quarter marked and a check payable to SCDOR (write your name, SSN, and "2026 SC1040ES" in the memo) to: SCDOR, IIT Voucher, PO Box 100123, Columbia, SC 29202. One hard rule sits over both routes: once you owe $15,000 or more in connection with any SCDOR return, South Carolina requires you to file and pay electronically under Code Section 12-54-250.

The SC2210 Penalty If You Underpay

Each installment's shortfall accrues simple interest at the underpayment rate, per day, from its due date until paid, computed on the SC2210 with your return; the latest form applies 7% across its rate periods, and the SCDOR adjusts the rate quarterly in step with the federal underpayment rate. Payments you do make are applied to the oldest underpayment first.

The day-count math stays small if you act fast. Skip a $392 June installment and pay it September 15 (92 days): $392 × 7% × 92/365 ≈ $7. Carry it to an April 15, 2027 filing (304 days) and it grows to about $23, and proportionally more on bigger vouchers. Three repair tools can shrink or erase the number: the annualized income method (federal Schedule AI computed for South Carolina) when income arrived unevenly, treating withholding as paid on its actual dates when that helps, and a written waiver for casualty, disaster, retirement after age 62, or disability. The federal penalty guide walks the parallel IRS computation on Form 2210.

What H. 4216 Does NOT Change

• The due dates. All four SC1040ES dates and the 25% split are untouched
• The $100 trigger. The prepayment rule and the SC2210 test work exactly as before
• Your federal payments. IRS quarterly amounts follow their own rules; see the federal quarterly guide
• The 0% bracket — because it's gone. Under the old schedule the first $3,560 of taxable income was tax-free; in 2026, tax starts at 1.99% from the first dollar. Low-income filers can owe slightly more under the new structure even as most bills shrink

Common Mistakes to Avoid

1. Autopiloting 100% of your 2025 tax

Safe, but expensive this year. Darnell's version of the mistake costs $941 in payments the state would eventually refund. Recompute 2026 under the two-rate structure before the September 15 voucher, not at filing time.

2. Projecting with the federal standard deduction

South Carolina no longer starts from your federal deduction. The SCIAD replaces it and phases out with income, so a single filer near $95,000 gets nothing while the federal return still shows a $16,100 standard deduction. Estimates built on the old federal-taxable-income starting point can miss by thousands of dollars of deduction.

3. Assuming the 0% bracket still shields small side income

It doesn't exist anymore. A retiree with $6,000 of untaxed consulting income who owed South Carolina nothing under the old schedule can now cross the $100 prepayment line without noticing.

4. Mailing a voucher for a quarter already paid online

The SC1040ES instructions ban it for a reason: a mailed duplicate creates a second payment record the SCDOR has to reconcile against MyDORWAY, and refund timing suffers while it does.

Georgia ran the same play this year on a different field: a mid-year rate cut to 4.99% that makes January voucher math obsolete. The Georgia estimated tax guide covers that recalculation.

Lower Rates, Right Payments: How Jupid Helps

Rate rewrites like H. 4216 punish anyone running quarterly taxes on last year's spreadsheet. Jupid works from the current numbers instead: it connects to your bank accounts, categorizes income and expenses with 95.9% accuracy, and keeps your South Carolina and federal projections in sync with what you've actually earned. Ask the AI accountant in WhatsApp or iMessage "what should my September 15 payment be?" and the answer already reflects the new rates, your withholding, and the cheaper of the two safe harbors. Try Jupid.

Action Checklist

• Recompute your 2026 South Carolina tax with the 1.99%/5.21% rates and your SCIAD amount
• Compare 90% of that number against 100% (or 110%) of your 2025 tax; pay the smaller on schedule
• Missed April or June? Pay the shortfall through MyDORWAY today to stop the per-day accrual
• Make the September 15 payment — state and federal Q3 land the same day
• Mark the quarter box on any mailed SC1040ES, and never mail one for a quarter paid online
• Owe $15,000+? Move everything to electronic filing and payment now (SC Code 12-54-250)
• Books closing early? File and pay by January 31, 2027 to erase the last installment

Sources

• SCDOR: Information about H. 4216 — the 1.99%/5.21% rates, effective dates, automatic future reductions
• 2026 SC1040ES, Individual Declaration of Estimated Tax — MyDORWAY steps, mailing address, the $15,000 electronic mandate
• SC2210, Underpayment of Estimated Tax — the $100 rule, safe harbors, due dates, penalty computation, waivers
• S.C. Revenue and Fiscal Affairs Office: H. 4216 fiscal impact — SCIAD amounts and phase-out ranges
• IRS: Form 1040-ES — the federal quarterly schedule running alongside South Carolina's

This guide is for general educational purposes and does not constitute tax, legal, or accounting advice. Estimated tax requirements depend on your income mix, residency, filing status, and withholding, and South Carolina's top rate can change again through H. 4216's revenue triggers. For advice specific to your situation, consult a qualified tax professional or the South Carolina Department of Revenue at dor.sc.gov.