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US quarterly estimated tax calculator (safe harbor)

To avoid the IRS underpayment penalty for 2026, your withholding and estimated payments generally need to reach the smaller of 90% of your 2026 tax or 100% of your 2025 tax, or 110% if your 2025 AGI was over $150,000 ($75,000 married filing separately). This calculator splits that minimum across the four 2026 due dates.

This calculator runs in your browser and needs JavaScript. The method is written out below if you want to do the sum by hand.

Last year (2025 return)

The “total tax” line of Form 1040.

This year (2026)

Leave empty to use last year only.

From a salary or other job, if any.

Nothing you type here is sent anywhere: the calculation runs on this page, in your browser.

How it is worked out

  1. Prior-year amount = 100% of your 2025 total tax, or 110% if your 2025 AGI was over $150,000 ($75,000 if married filing separately in 2026). It counts only if your 2025 return covered all 12 months.
  2. Current-year amount = 90% of the 2026 total tax you expect, if you enter it.
  3. Required annual payment = the smaller of the two, less tax withheld in 2026.
  4. Each payment = a quarter of that, in whole cents; any leftover cent goes on the last payment.

This is the minimum to avoid an underpayment penalty under the safe harbor rule in Publication 505, not a forecast of what you will owe. If your 2026 tax turns out higher, you still owe the difference when you file. Some people, such as farmers and fishermen, have different rules. State estimated tax is not included.

ReckonOS shows the four periods and estimates what to set aside from each payment you receive. US tax rules we apply.

Estimates based on the rules for the United States (federal estimated tax, 2026) as of November 2026. Check with your accountant. This tool gives an estimate, not tax, legal or financial advice. Sources: IRS Publication 505 (2026) (opens in a new tab); IRS Form 1040-ES (2026) (opens in a new tab).

More free tools: see all six.

Questions

What is safe harbor for US estimated tax?

Safe harbor, in US estimated tax, is the minimum you can pay across the four quarterly instalments to avoid an IRS underpayment penalty: 90% of this year’s tax, or 100% of last year’s tax (110% if last year’s adjusted gross income was over $150,000, or $75,000 if married filing separately).

When are the 2026 estimated tax payments due?

April 15, 2026, June 15, 2026, September 15, 2026 and January 15, 2027, according to Form 1040-ES (2026). A date that falls on a weekend or legal holiday moves to the next business day.

Does this calculator work out my 2026 tax?

No. It works out the minimum safe harbor payment from last year’s tax, and from this year’s if you enter an estimate. Working out the tax itself depends on your income, deductions and state, which is a job for your accountant or tax software.

Set aside tax from every payment as it arrives.

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