With $80,000 of profit, last year's tax of $8,000, and prior AGI of $60,000, the safe harbor is $8,000.00. That is 100% of last year's tax, because it is smaller than 90% of this year's estimate.
Safe-harbor amount
$8,000.00
The safe-harbor amount is $8,000.00.
How the total splits
Each voucher is one quarter of the smaller of 90% of this estimate and 100% of last year's tax, after withholding. The January voucher absorbs the rounding cent. The 20% QBI line is the simplified deduction: 20% of profit after the deductible half of self-employment tax, and at least $400 when that profit is $1,000 or more, capped at 20% of taxable income before the deduction. It does not apply the W-2 wage or specified-service limits. QBI does not reduce self-employment tax.
| This year's estimated tax | $16,647.46 |
|---|---|
| Safe-harbor amount | $8,000.00 |
| April 15, 2026 | $2,000.00 |
| June 15, 2026 | $2,000.00 |
| September 15, 2026 | $2,000.00 |
| January 15, 2027 | $2,000.00 |
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Pay the smaller of 90% of this year's tax and 100% or 110% of last year's tax, after withholding.
The 100% rule uses last year's total tax when that return covered 12 months. It becomes 110% when 2025 AGI was over $150,000, or over $75,000 if you will file married filing separately for 2026. The 90% rule uses this year's estimated tax. You pay the smaller one.
Withholding counts first. If it already covers the smaller harbor, the voucher is zero. If the balance after withholding is under $1,000, no estimated payment is required. Enter last year's tax as zero only when that full-year return had no tax.
| This year's tax | $16,647.46 |
|---|---|
| Safe harbor | $8,000.00 |
Only when prior AGI was at or under $150,000 ($75,000 if you file married filing separately this year) and that return covered a full year. Above that, the prior-year harbor is 110%. If 90% of this year is smaller, you can pay that instead.
A full-year return with zero tax means no estimated payment is required this year. Type zero only if that is what the return showed. A year you did not file is not the same thing.
It stops the underpayment penalty on the difference. You still pay the remaining tax with the return. This page does not compute the penalty interest rate.