How much should you send the IRS each quarter? Get your safe-harbor number and the four due dates — free, no signup.
Underpaying quarterly taxes triggers IRS penalties. This calculator uses the IRS safe-harbor rule — the amount that shields you from an underpayment penalty — plus your self-employment tax, so you know exactly what to pay and when.
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Total tax from last year's return (Form 1040, line 22) — the basis for the safe harbor.
From last year's return (Form 1040, line 11). The safe harbor rises to 110% of last year's tax if this was over $150,000 — or over $75,000 if married filing separately.
Your business net profit for the year (Schedule C net, or your share of S-corp/partnership SE income). Used for the self-employment tax estimate.
W-2 withholding from you or a spouse. Subtracted from the safe-harbor total before dividing into quarters.
Estimate only. AI Tax Accountant is a software tool, not a CPA firm, and this is not tax advice. The safe harbor is based on your prior-year tax; your actual liability may be higher or lower. Confirm your figures and any payments with your CPA or the IRS.
Upload your bank statements and AI Tax Accountant produces GAAP-formatted financials, a tax-strategy memo, and a deduction analysis from your actual numbers — so your estimated payments reflect reality.
The simplest safe approach is the IRS safe harbor: pay 100% of last year's total tax (110% if your AGI is over $150,000), split into four equal quarterly payments, minus any withholding. This calculator does that math for you and shows the four due dates. Confirm with your CPA.
For the 2026 tax year the federal due dates are April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027. If a date falls on a weekend or holiday, the deadline moves to the next business day.
The safe harbor is the amount that shields you from an underpayment penalty even if you end up owing more. It's the smaller of 90% of this year's tax or 100% of last year's tax — 110% if your prior-year AGI was over $150,000. Paying the safe-harbor amount in equal quarterly installments avoids the penalty. This calculator uses the prior-year method (100%, or 110% for higher incomes).
Self-employment tax is 15.3% (12.4% Social Security up to the annual wage base, plus 2.9% Medicare) on 92.35% of your net self-employment income. It's separate from and in addition to income tax. This tool estimates the self-employment portion; your full liability also includes income tax.