IRS Late Payment Penalty Estimator

Estimate how quickly IRS failure-to-pay penalties and interest add up once your balance drifts past the filing deadline. Enter the unpaid balance and days late to surface the monthly penalty applied, the interest accrual, and the all-in payoff amount you should prepare to wire or set up on an installment agreement.

Outstanding balance shown on your Form 1040, notice, or IRS transcript.
Count calendar days after the filing deadline or notice due date.
Defaults to 0.50% per month, the IRS standard when no levy notice is outstanding.
Defaults to 8.00% annual interest, approximating the current federal short-term rate + 3%.

This estimate is for planning purposes only. Verify penalty and interest calculations with your official IRS notice or tax professional.

Examples

  • $12,500 balance, 90 days late, defaults for rates ⇒ Failure-to-pay penalty (1.50% of balance): $187.50 • Estimated interest over 90 days: $246.58 ($2.74 per day) • Projected total due (tax + penalties + interest): $12,934.08
  • $28,000 balance, 240 days late, 0.25% monthly penalty, 7% interest ⇒ Failure-to-pay penalty (6.00% of balance): $1,680.00 • Estimated interest over 240 days: $1,282.74 ($5.34 per day) • Projected total due (tax + penalties + interest): $30,962.74

FAQ

Does the calculator include the separate failure-to-file penalty?

No. This tool isolates the failure-to-pay penalty. If you filed after the deadline without an extension, layer in the 5% per month failure-to-file charge separately.

How are partial months treated?

The IRS counts any partial month as a full month when computing the failure-to-pay penalty. The model mirrors that rule by rounding days late up to the next whole month.

Can I change the interest rate after the IRS announces a new quarter?

Yes. Update the optional IRS interest rate field with the blended annual rate for your delinquent period. The calculator will immediately restate the interest and total due.

What if I enter into an installment agreement?

Once an installment agreement is approved, the failure-to-pay rate typically drops to 0.25% per month. Enter 0.25 in the penalty field to see how the reduced rate changes your payoff timeline.

Additional Information

  • The failure-to-pay penalty accrues at 0.50% per month (or part of a month) and is capped at 25% of the unpaid balance by statute.
  • Interest compounds daily at the federal short-term rate plus 3 percentage points; the default 8.00% annual assumption mirrors early 2025 IRS notices.
  • Interest also begins accruing on penalty amounts once they post—use the per-day estimate to approximate the incremental cost if you cannot pay immediately after the quoted window.

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