About this tool
Why it exists.
When a client pays late, you may be entitled to charge interest, depending on your contract and local law. Working out the exact figure for each late invoice is fiddly. This calculator does the sum from the dates.
Enter the invoice amount, the annual interest rate, the due date and the date to calculate to. It counts the days overdue, applies simple daily interest and adds any fixed fee you enter. The rate and fee must come from your contract or the rules that apply to you, for example statutory late payment rules for business debts in your country.
How to use it.
- Enter the overdue amount and the annual interest rate.
- Choose the due date and the date you are calculating to.
- Add a fixed late fee if one applies, then read the interest and total.
Good questions.
How is late payment interest calculated?
Simple interest: amount × annual rate ÷ 365 × days overdue. This tool uses that method, without compounding.
What rate can I charge?
It depends on your contract and on the law where you work. Some countries set a statutory rate for business-to-business debts, often a margin above a central bank rate, so check the current official figure.
Is this legal advice?
No. It is an arithmetic aid. For disputes, large debts or unclear contracts, ask a qualified adviser.