Free calculator · tax year 2026
Estimated tax safe harbor calculator
The least you need to withhold or pay for the year so the IRS charges no underpayment penalty, whether the 100% or 110% rule applies, and what is still missing.
Still to withhold or pay for 2026: $5,400.
Still to withhold or pay for 2026$5,400110% of last year’s tax, $15,400, is lower than 90% of this year’s, $19,800, so $15,400 is the least to withhold or pay for 2026. You have $10,000 withheld and paid, $5,400 short. Extra withholding before December 31 counts as paid evenly through the year and closes the gap for every quarter; an estimated payment only counts from the day you make it.
| 110% of last year’s tax | $15,400 |
| 90% of this year’s tax | $19,800 |
| Safe harbor: the lower of the two | $15,400 |
| Each quarter, if paid as estimates | $3,850 |
| Withheld and paid so far | $10,000 |
| Still to withhold or pay | $5,400 |
Meeting the safe harbor avoids the penalty, not the tax: whatever is still owed is due by the April filing date. Married filing separately uses $75,000 for the 110% test, which this calculator does not ask.
Calculations, not tax, legal or investment advice.
Safe harbor rules for estimated tax: 90%, 100% and 110%
- Pay at least 90% of this year’s tax through withholding and estimated payments, or
- 100% of last year’s total tax, or 110% if last year’s AGI was over $150,000 ($75,000 married filing separately).
- Whichever is lower is your safe harbor. Last year’s number is the one you know for sure, which is why most people use it.
- No penalty at all if this year’s tax less withholding is under $1,000, or if last year was a full year with no tax.
Estimated tax due dates for 2026
| Income earned | Payment 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 |
Each payment covers a quarter of the safe harbor amount. Paying late in the year does not cover the earlier quarters: a January payment stops the penalty from that day on, not back to April.
Why retirees often withhold instead of paying estimates
Withholding counts as paid evenly through the year, whenever it actually happens. Have tax withheld from an IRA withdrawal or RMD in December and it covers April, June and September as well. That makes December the time to fix a shortfall, for example after a Roth conversion.
Social Security can withhold 7%, 10%, 12% or 22% with Form W-4V. A pension uses Form W-4P, and an IRA custodian takes withholding instructions with each withdrawal.
Method and sources
The required annual payment is the lower of 90% of this year’s tax and 100% of last year’s, or 110% when last year’s AGI was over $150,000. No penalty applies when this year’s tax less withholding is under $1,000, or when last year was a full year with no tax. The calculator checks the year as a whole; the penalty itself is figured quarter by quarter on Form 2210.
Tables and sources
- 26 U.S.C. §6654§6654(d)(1)(B): required annual payment is the lesser of 90% of the tax for the year or 100% of the tax shown on the prior year’s return; (d)(1)(C): 110% when prior-year AGI exceeded $150,000; (e)(1): no addition when the tax less withholding is under $1,000; (e)(2): none when the prior year showed no tax; (g): withholding is treated as paid in four equal parts on the installment dates unless the taxpayer elects otherwise · 2026 · www.law.cornell.edu
- IRS Publication 505, Tax Withholding and Estimated TaxChapter 4, Underpayment Penalty: general rule (90% / 100%), higher income taxpayers (110% above $150,000 AGI), and withholding treated as paid evenly · 2026 · www.irs.gov
- Instructions for Form 2210Who must pay the underpayment penalty; required annual payment; installment due dates April 15, June 15, September 15 and January 15 · 2026 · www.irs.gov
Retiree tax calculatorWork out this year’s federal tax from your Social Security, pensions, withdrawals and investment income.
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