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Tax Penalty & Interest Calculator (2025)

Calculate IRS failure-to-file and failure-to-pay penalties plus compounding interest on unpaid taxes. See monthly accrual and total amount owed.

$

Total Owed

$6,478

$6,478

Total Owed

FTF Penalty

$1,125

FTP Penalty

$150

Interest

$203

Summary

IRS penalties and interest bring your total from $5,000 to $6,478 after 6 months. Filing on time - even without full payment - significantly reduces penalties.

The Failure-to-File penalty is 5% of unpaid taxes per month (or partial month), up to a maximum of 25% of the tax owed.

The Failure-to-Pay penalty is 0.5% of unpaid taxes per month, also capped at 25%. It applies even if you filed on time.

When both penalties apply in the same month, the FTF penalty is reduced by the FTP amount, so the combined rate is 5% (not 5.5%) per month.

The IRS charges interest on unpaid tax plus accumulated penalties. The rate is the federal short-term rate plus 3%, compounding daily.

FTF Penalty: $1,125

Monthly Accrual

6 rows

MonthFTF PenaltyFTP PenaltyInterestCumulative
1$225$25$33$5,283
2$225$25$34$5,567
3$225$25$34$5,851
4$225$25$34$6,135
5$225$25$34$6,419
6$0$25$34$6,478

Estimate based on IRS penalty and interest rules. Actual interest is compounded daily. Does not account for penalty abatement, installment agreements, or offers in compromise. Not tax advice.

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