BadCop › Late-fee calculator
Invoice late-fee calculator
Work out the late fee on an overdue invoice using simple monthly interest, the way most freelance and small-business contracts phrase it ("1.5% per month on overdue balances"). Enter your own terms; this page does not tell you what you are allowed to charge.
18.75 late fee
Balance due: 1,268.75
What it costs by day
| Days overdue | Late fee | Balance due |
|---|
Formula: amount × (rate ÷ 100) × (days overdue ÷ 30) + flat fee, applied once the grace period has passed. This is what BadCop uses. If your contract says "per month or part thereof", round the months up instead.
Before you charge a fee
- It has to be in your terms. A late fee that was never agreed is unenforceable and will cost you the client. Put it in the contract and on the invoice.
- Know your jurisdiction. Some places cap interest on commercial debt; some (the UK, the EU) set a statutory rate you can claim even without a clause. See the rules by country. This page is not legal advice.
- State it before you apply it. Mention the terms in the firm reminder, apply it in the final notice.
BadCop applies exactly this calculation from your final-notice step onward, using the rate and grace period you configure. Get it on GitHub.