Calculator · tax year 2026
Estimated tax: the safe harbor amount
Enter the tax you expect this year, your withholding and last year's tax. The calculator finds the smaller safe harbor amount and splits what withholding does not cover across the four due dates.
Tax year 2026 Checked Review by
CheckedOct 19, 2026
The penalty for underpaying estimated tax does not ask whether you paid everything. It asks whether you paid enough, on time, through withholding and estimated payments. The amount that counts as enough is the required annual payment: the smaller of a share of this year's tax and a share of last year's tax.
If you pay at least that amount, in four equal installments by the due dates, there is no penalty even if you owe more when you file. This calculator works out that amount from your own numbers.
The calculator
This calculator runs in your browser with JavaScript. Without it, the steps under How the estimate works give the same result by hand, with the same figures.
Your entries stay on this device. Nothing you type is sent anywhere.
Your estimate
Enter your numbers and choose Estimate.
Estimates for education only, from the federal figures listed below. This is general information as of the date shown, not advice for your situation. The right answer depends on your facts, so check how it applies to your own situation before you act on it.
How the estimate works
The calculator follows these steps, in this order.
- This year's test: 90% of the total tax you expect for this year.
- Last year's test: 100% of the total tax on last year's return, or 110% if last year's adjusted gross income was over $150,000 ($75,000 if you file separately this year). It applies only if last year's return was filed and covered a full tax year.
- The required annual payment is the smaller of the two tests. Each of the four installments is 25% of it.
- Withholding counts as paid in equal parts on the four due dates, so subtract your expected withholding from the required annual payment and split what is left into four equal estimated payments.
- The due dates for this tax year are April 15, 2026, June 15, 2026, September 15, 2026 and January 15, 2027.
- Separately, if your total tax minus withholding is under $1,000, there is no penalty at all.
Where the rule comes from
The safe harbor is section 6654(d)(1) of the Internal Revenue Code, and the small-balance exception is section 6654(e)(1). The due dates for the year are printed on Form 1040-ES. The penalty is figured installment by installment, so paying the whole amount late in the year can still leave a penalty for the earlier quarters.
If your income arrives unevenly, the annualized income installment method on Form 2210 can lower the early installments. This calculator does not use it.
Worked example
Hypothetical example, not law and not a client
A single filer expects 30,000 dollars of total tax this year and 12,000 of withholding. Last year's return showed 24,000 of tax on AGI of 140,000, under the higher-income line, so the prior-year test is the full prior-year share: 24,000. This year's test comes to 27,000, so the required annual payment is the smaller, 24,000. Withholding covers 12,000 of it, which leaves 12,000 for estimated payments: 3,000 on each of the four due dates.
What this does not cover
- The annualized income installment method (Form 2210, Schedule AI) for income that arrives unevenly.
- The special share for farmers and fishermen, and the rules for estates, trusts and fiscal-year filers.
- Waivers of the penalty (casualty, disaster, retirement or disability) and the exception for people with no tax liability last year.
- The penalty amount itself, which is interest-like and depends on how late each installment is.
- State estimated tax.
Read more
Questions
If I pay the safe harbor amount, can I still owe tax when I file?
Yes. The safe harbor protects you from the underpayment penalty, not from the tax. If your tax this year is higher than the safe harbor amount, the rest is due by the filing deadline.
Why does withholding work differently from estimated payments?
Withholding is treated as paid in equal parts on the four due dates, whenever it was actually withheld, unless you elect otherwise on Form 2210. That is why extra withholding late in the year can fix an earlier shortfall, while a late estimated payment cannot.
Is this advice about my situation?
No. It is an estimate for education that shows how the rule works with the figures for the tax year. Your return depends on facts this page does not ask about, so check how it applies to your own situation before you act on it.
Figures used
Tax year 2026. Every figure the calculator reads comes from the verified library behind this site, with its source, the date it was checked and the date it is due for a re-check. If any figure passes its review date, the calculator pauses until it is re-checked.
| Figure | Value | Source | Checked | Review by |
|---|---|---|---|---|
Safe harbor shares (this year, last year, last year with higher AGI)cf-2026:estimated_tax.safe_harbor_pct | 90% of this year's tax; 100% of last year's tax, or 110% if last year's AGI was over the line | IRC 6654(d)(1)(B)(i)-(ii), 6654(d)(1)(C)(i) | CheckedOct 19, 2026 | |
Higher-income line for the prior-year test (last year's AGI)cf-2026:estimated_tax.high_agi_threshold | $150,000 ($75,000 married filing separately) | IRC 6654(d)(1)(C)(i)-(ii) | CheckedOct 19, 2026 | |
No penalty if the balance after withholding is undercf-2026:estimated_tax.penalty_threshold | $1,000 | IRC 6654(e)(1) | CheckedOct 19, 2026 | |
Each required installment, as a share of the required annual paymentcf-2026:estimated_tax.required_installment_pct | 25% | IRC 6654(d)(1)(A) | CheckedOct 19, 2026 | |
Due dates for the four installmentscf-2026:estimated_tax.due_dates | April 15, 2026; June 15, 2026; September 15, 2026; January 15, 2027 | IRS Form 1040-ES (2026) | CheckedOct 19, 2026 |