Late Payment Interest Calculator
Estimate interest owed on overdue invoices with customizable annual rates and simple or compound interest.
Use this calculator in your browser, review its inputs and assumptions, then continue to a full invoice or quote when ready.
How to use this calculator
Enter the invoice balance, due date, comparison date, and an annual rate. The calculator shows overdue days and estimated simple or daily-compounded interest; only charge interest when your agreement and applicable rules allow it.
Understand the result
The calculation runs in your browser and exposes its inputs so you can check the result. It is intended for planning and does not replace tax, legal, lending, or accounting advice.