2026 Quarterly Estimated Tax Calculator
Safe-harbor target and per-quarter payments for the self-employed
Enter your year-to-date self-employment income and this calculator projects your 2026 federal tax, applies the IRS safe-harbor rule (the smaller of 90% of this year's tax or 100% to 110% of last year's), and splits the result into the four quarterly payments with their due dates. Estimates only: it assumes a single filer with the standard deduction.
Quarterly Estimated Tax Calculator
Year-to-date business income after expenses
From a W-2 job or S-corp salary; counts toward the safe harbor
Enables the prior-year safe harbor, often the easiest to hit
Over $150,000 raises the prior-year safe harbor from 100% to 110%
Estimate only. Year-to-date income is annualized assuming an even pace through the year. Single filer, standard deduction, 2026 rates. W-2 wages, investment income, and the QBI deduction are not modeled, so the figure errs on the safe side. The safe harbor is the SMALLER of 90% of this year's tax or 100% (110% for higher income) of last year's tax.
How the safe harbor works
The IRS does not require you to predict your income perfectly. You avoid the underpayment penalty (IRC section 6654) by paying, through withholding and estimates, the smaller of two targets: 90% of the tax you will owe this year, or 100% of last year's total tax. If your prior-year adjusted gross income was over $150,000 ($75,000 married filing separately), the prior-year target rises to 110%.
Most people with a filed prior-year return use the prior-year harbor because it is a known number: pay a quarter of it each period and the penalty math is settled no matter how the year turns out.
California is different
California weights its installments 30% / 40% / 0% / 30% (Form 540-ES): nothing is due with the September federal installment, and the CA tax itself is computed on California's own brackets.
For the full picture, read our quarterly estimated taxes guide or check this year's due dates on the tax deadline calendar.
Disclaimer: This calculator is general information, not tax advice. Results are estimates based on 2026 federal rates for a single filer with the standard deduction; state tax, other income, and credits are not modeled. Using this tool does not create a client relationship with Arc & Ledger LLC.