Self-Employed Estimated Tax Calculator — 2026

Work out what you owe the IRS this quarter in about 30 seconds. Covers self-employment tax, the SE-tax deduction, QBI, and the four 2026–27 due dates.

Q3 2026 is due Monday, September 15, 2026. Underpay and the IRS charges interest-style penalties per quarter — there is no annual catch-up.

Your numbers

Suggested payment for Q3 — due Sep 15, 2026

Full-year estimate	Amount
Net earnings from self-employment (92.35%)
Self-employment tax (Social Security + Medicare)
Deduction: ½ of SE tax
Qualified business income (QBI) deduction
Standard deduction
Taxable income
Federal income tax
Total 2026 federal tax
Less withholding & estimates already paid
Still to pay across remaining quarters

Remaining 2026 due dates: Q3 — Sep 15, 2026 · Q4 — Jan 15, 2027. Pay free at IRS Direct Pay or EFTPS. State estimated tax is separate and not included here.

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The calculator above is a single snapshot. The Pro spreadsheet is the thing you actually run your year on — it keeps the numbers as they move.

Live 4-quarter worksheet — enter profit as it lands, every quarter re-forecasts itself
Safe-harbor planner — the 100% / 110% prior-year test worked out for you, so a big year can't produce a penalty
Full SE-tax breakdown — wage base cap, additional Medicare surtax, the half-SE deduction
Deduction & mileage tracker with the categories that map to Schedule C lines
2026 & 2027 rate reference and a payment log so you know exactly what you sent and when
Excel / Google Sheets / LibreOffice. No subscription, no account, instant download.

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How the estimated tax math actually works

1. Self-employment tax comes first

You pay both halves of Social Security and Medicare: 12.4% Social Security on net earnings up to the wage base ($184,500 projected for 2026), plus 2.9% Medicare with no cap, and a further 0.9% Medicare surtax above $200,000 single / $250,000 joint. Net earnings are 92.35% of your Schedule C profit, so a $85,000 profit is $78,497 of net earnings — that alone is about $12,010 of SE tax before a cent of income tax.

2. Then income tax, on a smaller number

Half your SE tax comes off your income, and most freelancers also take the 20% QBI deduction, then the standard deduction. Those three together are why your income tax bill is much smaller than your headline profit suggests — and why guessing at "30% of everything" usually overpays.

3. Safe harbor is the part that saves people

You avoid the underpayment penalty if you pay either 90% of what you end up owing for 2026, or 100% of your total 2025 tax (110% if your 2025 AGI was over $150,000) — whichever is smaller. If you're having a big year, paying last year's number is both cheaper and completely safe. That's the calculation the Pro planner does for you.

4. Quarters are not equal and not really quarterly

The IRS periods run Jan–Mar, Apr–May, Jun–Aug and Sep–Dec, due Apr 15, Jun 15, Sep 15 and Jan 15. Miss one and the penalty accrues from that date — catching up in December does not undo it.