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Late Fee Calculator

This calculator turns a due date, a paid date, and a rate into days late, a fee, and a new total. You can use a flat fee, a monthly percent, or an annual rate, simple or compounding. It does not look up a state cap. Late fee limits vary by state and by contract, so this is not legal advice.

Enter the invoice amount, the due date, and the date it was paid. Pick a flat fee, a monthly percent, or an annual rate.

Late fee limits vary by state and by contract, so check yours. This is not legal advice.

How to use the number

  1. Put the fee terms on the invoice before the work starts.
  2. Count days from the due date to the paid date, then subtract grace days.
  3. Copy the line this page writes and paste it on the next invoice or the reminder.
  4. If you need the letters, open the late-payment kit.

Simple monthly interest is the amount times the monthly rate times days divided by 30. Compounding uses that rate on the running balance. An annual rate uses 365 days. A flat fee is added once, and only when the invoice is actually late. The page does not store the amount.

Need to send the invoice itself?

Create a professional invoice that states your late-fee terms up front — free, no signup, no watermark. Open the free invoice generator →

Late fee FAQ

How much late fee can I charge?

A common policy is 1.5% per month (18%/yr) or a flat fee, but the legal maximum depends on your country/state and your contract. State your late-fee terms on the invoice before the work, so they're enforceable.

How is the interest calculated?

Simple interest is the amount times the rate times the late days. Compounding grows the fee on the running balance. Grace days are skipped. A flat fee is added once, only if the invoice is late.

Should I actually charge it?

Often the threat is enough. A clear, polite reminder that mentions the accruing late fee gets most invoices paid. Stating the policy on the invoice up front is what makes it work — create one free with PaidPilot's generator.