KitebillLate fee calculator for overdue invoices
Work out how late an invoice is and what your agreed late fee comes to: a flat fee, a one-time percentage, a monthly percentage or yearly interest. You get a ready-to-paste line for your reminder email.
How the numbers work
- Days late = payment date (or today) minus due date. Paying on the due date counts as not late.
- Chargeable days = days late minus your grace period. If that's zero, there's no fee.
- % per month uses pro-rata simple interest with a 30-day month. % per year uses simple interest over a 365-day year. A one-time % or flat fee applies once the grace period is over.
- Amounts are rounded to 2 decimals. The tool doesn't compound interest.
Before you charge a late fee
A late fee only works if your client agreed to it in advance. Put it in your contract and print it on every invoice, for example: "Payment due within 15 days. Late payments incur 1.5% per month." Some countries set a statutory interest rate for late business payments, and others cap or restrict late fees, so check the rules where you and your client are. This page is not legal or tax advice. Our late fee invoice guide covers wording and when it's worth it.
Often a polite reminder on the due date does more than a fee. If invoices keep slipping, track them: the free Kitebill app flags sent invoices as overdue automatically, keeps everything in your browser, and Pro is US$29 once.