| Prior-year door, 100% | $12,000 × 100% | $12,000 |
| Current-year door, 90% | $15,000 × 90% | $13,500 |
| Required to be safe | the smaller of the two | $12,000 |
The four payment periods
| Jan 1 – Mar 31 | April 15, 2026 | $3,000 |
| Apr 1 – May 31 | June 15, 2026 | $3,000 |
| Jun 1 – Aug 31 | September 15, 2026 | $3,000 |
| Sep 1 – Dec 31 | January 15, 2027 | $3,000 |
- The second period is two months long and the fourth is four. Paying after each calendar quarter is late in June, every year.
- Paying the safe harbour still leaves about $3,000 due at filing — safe from the penalty is not the same as paid in full.
- Under $1,000 owed at filing and the penalty does not apply at all.
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The figures this uses
| Figure | 2026 | Source |
|---|---|---|
| Estimated tax | generally required if you expect to owe $1,000 or more. Safe harbour: 90% of the current year's tax or 100% of the prior year's, whichever is smaller | irs.gov |
| Estimated tax safe harbour, higher income | 110% of the prior year's tax when prior-year AGI was over $150,000 ($75,000 if married filing separately) and less than two-thirds of income is from farming or fishing | irs.gov |
| Estimated tax payment periods | Jan 1-Mar 31 due April 15 · Apr 1-May 31 due June 15 · Jun 1-Aug 31 due September 15 · Sep 1-Dec 31 due January 15. The penalty is figured separately for each period | irs.gov |
How the calculation works
Estimated tax is not a guess at this year's bill. It is a choice between two amounts, and paying the smaller one on time protects you from the underpayment penalty. The calculator works out both.
- The prior-year amount. Last year's total tax, from your return, at 100%. If last year's adjusted gross income was over $150,000 ($75,000 married filing separately), it becomes 110%.
- The current-year amount. Your forecast of this year's tax, at 90%.
- What you must pay. The smaller of the two. The prior-year amount is the one you can know for certain in January, which is why it is the usual choice.
- Less withholding. Tax withheld from wages during the year counts, and it is treated as paid evenly across the four dates.
- Each payment. What is left, divided by four, due on:
| Period | Due |
|---|---|
| January 1 to March 31 | April 15, 2026 |
| April 1 to May 31 | June 15, 2026 |
| June 1 to August 31 | September 15, 2026 |
| September 1 to December 31 | January 15, 2027 |
The penalty is figured separately for each period, so paying the full amount late in the year does not cure an earlier one. If you will owe less than $1,000 when you file, the penalty does not apply at all.
What it leaves out
- The annualized income installment method, which lets the payments follow your income when it arrives unevenly. See estimated taxes.
- The farmers' rule, under which a farmer who files and pays by the March deadline makes no estimated payments at all. See the farmer's March 1 rule.
- State estimated tax, which follows each state's own rules.
The deadlines calendar shows which of the four dates move when they fall on a weekend or holiday.
Common questions
Which of the two amounts do I have to pay?
Why is my prior-year figure 110%?
Does paying the safe harbour mean I owe nothing in April?
Why are the payments not every three months?
This calculator is for educational purposes only and does not constitute tax, legal, or financial advice. It covers United States federal tax and simplifies in the ways noted beside each result. Consult a qualified tax professional about your situation.