Your paycheck withholds tax on your salary — but most S corp income isn't salary. The safe-harbor rule that makes year one penalty-proof, the December withholding trick, and the four dates that matter (one of them is in 2027).
The first year after an S corp election has a predictable plot twist. You set up payroll, take a reasonable salary, watch taxes come out of every paycheck, and assume you’re covered — then your tax preparer tells you in March that you owe five figures, plus an underpayment penalty. Nothing went wrong with the election. What went wrong is that your paycheck only withholds tax on your salary, and most of an S corp owner’s income isn’t salary.
An S corporation pays no federal income tax itself. All profit flows to your personal return on a K-1 — and unlike wages, nothing is withheld from it. If your company earns $200,000 and your salary is $90,000, roughly $110,000 of profit lands on your 1040 with zero tax paid in along the way. The IRS expects tax on that income during the year, not in April. That’s what quarterly estimated payments are for, and with the underpayment rate at 7%, compounded daily, skipping them is genuinely expensive now — not the rounding error it was a decade ago.
You never have to predict your income perfectly. You just have to pay in — through withholding plus estimates — the lesser of:
For a first-year S corp owner, the prior-year number is the gift: it’s a known figure sitting on last year’s Form 1040. Pay 100% (or 110%) of it in four even installments and you are penalty-proof — even if the business has a monster year and you owe a large balance in April. You’ll still owe the tax, but not a dollar of penalty, and you’ll have had the cash working for you all year.
| Payment | Covers | Due |
|---|---|---|
| Q1 | Jan–Mar | April 15 |
| Q2 | Apr–May | June 15 |
| Q3 | Jun–Aug | September 15 |
| Q4 | Sep–Dec | January 15 (2027 for this year’s Q4) |
Note the rhythm: the “quarters” are 3, 2, 3, and 4 months long. Q2 arrives fast, and Q4 comes after the year ends — the last chance to fix a shortfall for 2026 is January 15, 2027.
Estimated payments are credited when paid — miss Q2 and a big Q4 check doesn’t erase the penalty for the middle of the year. But W-2 withholding is treated as if paid evenly across the whole year, no matter when it actually happened. Since you control your own payroll, you can crank up federal withholding on your November and December paychecks (even withhold nearly an entire bonus) and the IRS treats it as if you’d paid it since January. It is the single most effective way to repair an underpayment discovered late in the year — and it only works before December 31.
Landscapers, tax practices, e-commerce sellers with a Q4 spike — anyone whose profit arrives unevenly can use the annualized income method (Form 2210, Schedule AI) to match each quarter’s payment to what was actually earned by then. It’s paperwork, but it stops the IRS from pretending your December revenue arrived in March.
Most states run their own estimated-payment system with their own penalties. And if your state offers a pass-through entity tax (PTET) election — the SALT-cap workaround — those payments come from the company, on the state’s schedule, which changes how much you need to send personally. Several states require the PTET election or an estimated PTET payment before year-end, so this belongs in the same conversation as your Q4 estimate, not after it.
The first year of an S corp is when the habits form. Owners who set the safe-harbor autopay in year one never think about penalties again; owners who wing it usually pay the IRS an involuntary 7% tip.
Talk it through with a licensed US tax professional — we'll tell you honestly whether it applies to your situation.
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