Estimated Tax Safe Harbor
How much has to be paid in this year to avoid the underpayment penalty, and how far short am I? Every piece below can be linked to, so it opens in a window on your reader's screen, current as of the record. No form to fill in.
2026 law · Reviewed September 6, 2026 · The full page, with methodology and sources · the terms · All tools
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Last year's tax and income, this year's expected tax, and what is being withheld and paid in; the safe harbor, the shortfall, and the year-end withholding that closes it out. In a frame it carries no cookies, no tracking, and a visible link back to the methodology. Your site has to allow frames; most do. The link that opens it in a small window is on the professionals page.
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- In plain words.
- The IRS expects tax to be paid as you go, through withholding or quarterly payments. If you pay in too little during the year there is a penalty, even if you pay the balance in April. The safe harbor is the amount that avoids the penalty: the smaller of 90 percent of this year's tax or all of last year's tax (110 percent if last year's income was high). This tool computes that amount, how far short you are, and the withholding that would fix it.
- Why it matters.
- In a year with a big Roth conversion or a sale, this year's tax jumps but last year's figure still counts as safe. And money withheld from an IRA withdrawal in December counts as if it were paid all year, which a quarterly payment does not.
- An example.
- Last year's tax was $20,000; this year's will be $40,000; $15,000 is being withheld. The safe harbor is $20,000, so $5,000 more withheld before December 31 avoids the penalty. The other $20,000 is still due in April, without a penalty.
- Where it stops.
- It covers individuals on a calendar year. It does not compute the penalty itself, or the method for income that arrives unevenly, and state estimated tax is separate.
The facts
Six quotable sentences on the estimated-tax safe harbor.
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- No underpayment addition applies if the amount paid in during the year, through withholding and timely estimates, is at least the lesser of 90 percent of this year's tax or 100 percent of last year's (§ 6654(d)(1)(B)).
- If last year's adjusted gross income was above $150,000 ($75,000 married filing separately), the prior-year figure is 110 percent instead (§ 6654(d)(1)(C)).
- Nothing is owed either way if the tax left after withholding is under $1,000 (§ 6654(e)(1)).
- Withholding is treated as paid in equal parts on the four due dates whenever it was actually withheld (§ 6654(g)). An estimated payment counts only when made. So a withholding from an IRA or pension distribution in December cures a whole year's shortfall; a December estimate cures only the last quarter's.
- Example: last year's tax was $20,000; this year, with a large conversion or sale, it will be $40,000. The safe harbor is $20,000, the prior-year figure, not $36,000. With $15,000 withheld, $5,000 more withheld before December 31 makes the year safe; the remaining $20,000 is simply due with the return.
- The due dates are April 15, June 15, September 15, and January 15 of the next year. A first-year retiree with no withholding on a new pension is the classic underpayer; the fix is a Form W-4P.
The safe harbor
The rule, the high-income variant, the de minimis test, and the withholding treatment in one table.
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| Rule | Figure | Authority |
|---|---|---|
| Required annual payment | Lesser of 90% of this year's tax or 100% of last year's | § 6654(d)(1)(B) |
| If last year's AGI exceeded | $150,000 ($75,000 separate): 110% of last year's tax | § 6654(d)(1)(C) |
| No addition if the balance due is under | $1,000 | § 6654(e)(1) |
| Withholding is treated as paid | In equal parts on each due date, whenever withheld | § 6654(g)(1) |
| Due dates | April 15; June 15; September 15; January 15 of the next year | § 6654(c) |
Cite and link.
The clean address, a citation generated from the record so it can never carry a stale review date, and an address for every section so you can point a reader at the exact table or method.
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- Link
- https://consideratecapital.com/tools/estimated-tax-safe-harbor
- Citation
- Considerate Capital, "Estimated Tax Safe Harbor," reviewed September 6, 2026, https://consideratecapital.com/tools/estimated-tax-safe-harbor.
Link to a section
- The calculator https://consideratecapital.com/tools/estimated-tax-safe-harbor#calculator
- The facts https://consideratecapital.com/tools/estimated-tax-safe-harbor#facts
- The rule https://consideratecapital.com/tools/estimated-tax-safe-harbor#key-numbers
- How the harbor works https://consideratecapital.com/tools/estimated-tax-safe-harbor#how-it-works
- Methodology https://consideratecapital.com/tools/estimated-tax-safe-harbor#methodology
- Sources https://consideratecapital.com/tools/estimated-tax-safe-harbor#sources
- Revision history https://consideratecapital.com/tools/estimated-tax-safe-harbor#revision-history
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