United States / Tools / Estimated tax safe-harbour calculator
Estimated tax safe-harbour calculator
The safe harbour is a published rule, not a forecast. Hit it and the underpayment penalty cannot reach you, whatever the year turns out to look like.
| You enter | last year's tax and AGI, and what you expect to owe this year. |
|---|---|
| It applies | the safe-harbour rule: the lesser of 90% of this year and 100% of last — or 110% if your AGI cleared $150,000. |
| You get | the quarterly instalment and the four due dates. This is the amount that stops a penalty, not a forecast of your bill. |
A worked example
Prior-year tax of $40,000 on AGI above $150,000 puts the safe harbour at 110% — $44,000 for the year, or $11,000 a quarter — even if this year turns out smaller. Pay that and the underpayment penalty cannot reach you.
Safe-harbour instalment, per quarter
- 90% of current-year tax
- $21,600.00
- 100% of prior-year tax
- $20,000.00
- Required annual payment (100% of prior-year tax)
- $20,000.00
Due dates: 15 April · 15 June · 15 September · 15 January (following year). A date falling on a weekend or legal holiday shifts to the next business day — not computed here.
An estimate, not a quote. The IRS produces the figure that actually applies to you — check there before you rely on a number. This is the safe harbour — the payment level that avoids an underpayment penalty. Hitting it does not mean the year's tax is fully paid; it only stops the penalty clock.
What this deliberately leaves out
Every input here is a figure you bring from your own return — this tool does not estimate your actual tax liability. Married-filing-separately individuals use a $75,000 AGI threshold instead of $150,000; that's noted, not modelled as a separate path. Farmers, fishermen, and household employers have their own rules (Form 1040-ES). Figures verified 2026-08-17.
What to do with this number: The safe harbour protects you from the penalty; it does not mean the year is paid. If this year runs well ahead of last, the balance is still due at filing — the safe harbour just stops it costing extra.
The figures behind this tool, with their sources and verification dates: the companion guide. When the statute or schedule changes, the guide and the tool move together.