Invoice Late Fee Calculator

FAQ

How do I calculate a late fee on an invoice?

Count the days past the due date, subtract any grace period, then add a flat fee, a one-time percentage of the invoice and/or interest: invoice amount × annual rate × days late ÷ 365. A rate of 1.5% a month is 18% a year — on a $1,000 invoice that's about $14.79 for 30 days.

What is a reasonable late fee for an invoice?

Common terms are 1–1.5% per month on the unpaid balance or a flat $25–$50 fee, after a 5–30 day grace period. The fee must be in your contract or invoice terms, and many US states cap interest rates, so check your local rules.

How much interest can I charge on a late payment in the UK?

For business-to-business invoices, the Late Payment of Commercial Debts (Interest) Act 1998 allows 8% plus the Bank of England base rate a year, plus fixed compensation of £40 (under £1,000), £70 (under £10,000) or £100 (£10,000 or more).

Can I charge a late fee if it wasn't in my contract?

In the US, usually not — late fees have to be agreed in advance. In the UK and EU, statutory interest and compensation apply to business-to-business invoices even if your contract doesn't mention them.

How do I write a polite overdue invoice email?

Give the invoice number, amount, due date and days overdue, show the fee breakdown, add a payment link and ask when you'll be paid. Start friendly, send a firm reminder a week later, then a final notice. The generator above writes all three.

This calculator gives estimates, not legal advice.