IRS Penalty & Interest Calculator - Late Tax Payment Estimate

Estimate approximate IRS penalties and interest on a late federal tax balance. This is an educational tool that uses simplified versions of the failure-to-file and failure-to-pay penalty rules plus interest on unpaid tax.

Original tax balance
Failure-to-file penalty
Failure-to-pay penalty
Interest on unpaid tax
Estimated total due now

This calculator uses simplified penalty rules: failure-to-file at 5% per month (capped at 25%) and failure-to-pay at 0.5% per month. Interest is approximated using a fixed annual rate compounded monthly on the original tax. Real IRS calculations can include overlapping rules, changing interest rates and additional details.

IRS Penalty & Interest Calculator Explained

This IRS penalty and interest calculator provides a simplified estimate of what someone might owe on a late federal income tax balance. It uses common penalty concepts such as failure-to-file and failure-to-pay, together with interest on the unpaid tax.

You can enter your unpaid tax balance, the number of months the return is late, the number of months the balance has remained unpaid, and an assumed annual interest rate. The calculator then estimates:

Failure-to-file penalty (modeled at 5% per month, capped at 25% of the tax balance)
Failure-to-pay penalty (modeled at 0.5% per month)
Interest on the unpaid balance using a fixed annual rate with monthly compounding
An approximate total amount due combining tax, penalties and interest

Real IRS calculations are more detailed: actual interest rates change over time, penalty interaction rules can overlap, and there may be additional penalty types or adjustments. This calculator is for educational and planning purposes only and is not official tax advice. For an exact payoff amount, taxpayers should contact the IRS directly or consult a tax professional.