Late Payment Interest Calculator
Work out simple interest on an overdue invoice from the amount, your rate and days overdue.
- Interest due
- —
Arithmetic only. Check your contract and current law before charging interest.
What is the Late Payment Interest Calculator?
The late payment interest calculator works out the simple interest due on an overdue invoice. You type the annual rate, so it follows your own terms. Enter the invoice amount and days overdue to see the interest and the total now due.
How it works
Interest equals the invoice amount multiplied by the annual rate divided by 100, multiplied by the days overdue and divided by the days in the year. Total due equals the invoice amount plus the interest. The tool uses simple, not compound, interest.
How to use it
- Enter the invoice amount.
- Enter the annual interest rate from your agreement.
- Enter the number of days overdue.
- Choose a 365 or 360-day year to match your terms, then read the total due.
Late Payment Interest Calculator — FAQ
Where do I get the interest rate?
Use the rate in your contract or invoice terms, or the rate required by applicable rules. This tool never assumes one.
Is this simple or compound interest?
Simple. Interest is calculated once on the invoice amount without adding interest to the base.
Can I charge interest without agreed terms?
That depends on your contract and the law. Check your written terms or take professional advice before charging interest.