IRS Late Filing and Late Payment Penalty and Interest Calculator

How to do it

1. 1
   Enter the tax owed

   Type the total tax, and any amount already paid through withholding or estimated payments.

2. 2
   Enter the dates

   Enter the original due date, the date you filed and the date you paid.

3. 3
   Tick an installment agreement if you have one

   The tool then uses the lower payment penalty rate.

4. 4
   Read the penalties

   See the failure-to-file and failure-to-pay penalties and whether the minimum applied.

5. 5
   Read the interest and total

   See the interest, the total extra cost and the total now due, then edit the rates if they change.

About this tool

If you file your tax return after the deadline or pay after the due date, the IRS adds penalties and interest to the tax you owe. This calculator takes the tax you owe, the due date, the date you filed and the date you paid, and estimates the failure-to-file penalty (5 percent a month, reduced by the failure-to-pay penalty), the failure-to-pay penalty (0.5 percent a month), the minimum penalty for returns more than 60 days late and the interest, compounded daily at the quarterly rates in an editable table. It shows how each part grows, so you can see what paying sooner would save.

Who this is for Taxpayers who missed the April deadline, people who filed on extension but could not pay, and anyone who received a notice with penalties and wants to check the numbers. It also shows the cost of waiting a few more weeks before filing or paying.

The failure-to-file penalty The penalty is 5 percent of the unpaid tax for each month or part of a month the return is late, up to 25 percent. In every month when both penalties apply, the failure-to-file part is reduced by the 0.5 percent failure-to-pay penalty, so the combined rate is 5 percent a month for the first five months, and the filing part stops at 22.5 percent. If the return is more than 60 days late, a minimum applies: the smaller of $525 (for returns due in 2026) or the full tax owed. The minimum is also editable.

The failure-to-pay penalty It is 0.5 percent of the unpaid tax for each month or part of a month after the due date, up to 25 percent. It falls to 0.25 percent a month when you have an approved installment agreement, and the tick box in the tool applies that rate. It grows even if you filed on time or on extension, because an extension to file is not an extension to pay.

Interest Interest is charged on the unpaid tax and on the penalties from the due date until payment, at the federal short-term rate plus 3 percentage points, set every quarter and compounded daily. The rate for individuals is 7 percent in most quarters of 2026 and 6 percent in the second quarter. The tool applies those rates day by day to the unpaid tax and shows the total. Interest on penalties is not included in this estimate, so the total may be slightly higher.

Worked example A taxpayer owes $6,000 after credits and withholding, was due on April 15, 2026 and filed and paid on October 15, 2026. That is seven months, counting part months. The failure-to-file penalty is 4.5 percent times seven, capped at 22.5 percent, or $1,350; the failure-to-pay penalty is 0.5 percent times seven, or $210; and the interest for 183 days is roughly $200. The extra cost is about $1,760, so the total due is about $7,760.

How to reduce the bill Pay as much as you can now, because both interest and the failure-to-pay penalty grow with the unpaid amount. File even if you cannot pay, since the filing penalty is ten times the payment penalty. If you have a reasonable cause, such as serious illness or a disaster, you can ask for penalty relief, and first-time abatement may be available if your record is clean.

Limits This is an estimate that follows the published rules. The IRS computes the exact amount and may adjust for relief and rounding. It is not tax advice.

Worked example

Tax owed of $6,000, due April 15, 2026, filed and paid on October 15, 2026: failure-to-file $1,350, failure-to-pay $210 and interest of about $200, an extra cost of about $1,760.