Estimate your balance due, penalties and interest
Before you extend, find out what you owe. This estimator shows your balance for 2026 and what late filing or late payment would add.
Reviewed October 30, 2026 against IRS.gov guidance. How we check facts.
Balance-due and late-payment estimator
For individual returns for tax year 2026, due April 15, 2027. Everything stays in your browser.
| Unpaid tax on April 15 | $2,000 |
|---|---|
| Failure-to-pay penalty | $0 |
| Failure-to-file penalty | $0 |
| Interest at 7% a year (IRS underpayment rate for individuals, fourth quarter of 2026) | $29 |
| Estimated total to pay | $2,029 |
An estimate, not a bill. The IRS calculates the exact amount, and interest also accrues on penalties. The interest rate is reset every quarter. Penalties can sometimes be removed for first-time or reasonable-cause relief.
How to get the two numbers it needs
- Total tax: the fastest estimate is last year’s total tax (line 24 of your 2025 Form 1040), adjusted for big changes in income. Tax software gives a precise figure.
- Payments by April 15: add the federal withholding on your W-2s and 1099s, your 2026 estimated tax payments, and anything you plan to pay with your extension.
The rules the estimator uses
- Failure to pay: 0.5% per month or part of a month on unpaid tax, up to 25%. Waived for the extension period if you paid at least 90% by April 15 and file by October 15.
- Failure to file: 5% per month or part of a month, reduced by the failure-to-pay penalty for the same month, up to 25%. With a valid extension it only applies after October 15.
- Interest: 7% a year compounded daily from April 15, 2027 to the date you pay. The IRS resets the rate each quarter, so the true figure may differ.
It doesn’t model the minimum penalty for returns more than 60 days late, interest on penalties, installment-agreement rates or state penalties.