Skip to Calculator
When you pay your taxes late, the IRS charges interest on any unpaid amount. The interest compounds daily from the due date of the return until the date you pay in full. This is true even if you have filed an extension. An extension only extends the time to file, but does not extend the time to pay.

The interest rate charged by the IRS is the federal short-term rate plus 3%.
The IRS determines the federal short-term rate every three months and then puts out an announcement about the new late payment interest rate.
For details about interest rates, visit the IRS News Release and Fact Sheet Archive and look for the most recent Internal Revenue release about interest rates or search “quarterly interest rates” on IRS.gov; the relevant interest rate is the rate for underpayments.

The IRS Interest Calculator below is only for individuals – married or single. It is not companies. The interest rate calculator is updated with the IRS interest rates through the end of the current quarter.

To use the IRS Interest Calculator, enter the amount of tax due, not including any penalties. The IRS does not charge interest on penalties. Pick the start date – the date your taxes were due – which is usually April 15th of the year you should have filed your tax return. Next, choose the end date which would be the date you plan to pay the entire amount. The latest date that you can select is the last day of the current quarter because the IRS has not published any interest rates beyond that time.

If you need help with back taxes, FATCA, FBAR or Streamlined Procedures, fill out the contact form on this page for a free evaluation.

Stay tuned for our upcoming IRS Penalty Calculators, IRS Payment Plan Calculators and more.