Invoice Late Fee Calculator
Figure out exactly how much late fee to charge (or how much you're owed) on an overdue invoice — enter your rate and days overdue.
Enter Your Numbers
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Enter your numbers and click Calculate to see the late fee owed.
How Late Fees Are Calculated
Most late fee clauses charge a percentage of the invoice amount per month (or a prorated daily equivalent) for every day or month payment is overdue:
Late Fee = Invoice Amount × Monthly Rate × (Days Overdue ÷ 30)
This calculator prorates the monthly rate by days, which is the most common approach — but always check what your specific contract or invoice terms state, since some agreements charge a flat fee per late month rather than a prorated daily rate.
A Few Things to Know Before Charging One
- The late fee rate and terms need to be stated clearly on the original invoice or contract — you generally can't add one retroactively after the fact
- Many jurisdictions cap interest/late fee rates (usury laws) — 1-1.5% per month (12-18% annualized) is a common, defensible range in the US, but confirm your local limits
- The goal is deterrence, not revenue — a clearly stated late fee changes customer payment behavior even if you rarely have to actually collect it
Want the full system for getting paid faster in the first place? Read our guide on invoice best practices or managing unpaid invoices.
Tired of chasing invoices manually?
We build systematic AR follow-up processes so you rarely need a late fee clause at all.
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