Late Fee & Interest Calculator
How much can you charge on an overdue invoice? Enter the amount, due date and agreed rate, and see the days overdue, accrued interest and total owed below. Everything is calculated in your browser.
- Days overdue0 days
- Principal$0.00
- Interest$0.00
- Fixed late fee$0.00
How do you calculate late fees and interest?
The most common approach charges interest on the principal, by annual rate and days overdue: interest = principal × annual rate ÷ 365 × days overdue. Many contracts add a fixed late fee on top. If the contract specifies compounding, it can be rolled up daily.
How much can I actually charge?
That depends on the late-payment terms in your contract and any local cap on penalties. Without a written agreement you can usually only claim statutory interest — so spelling out the rate and late fee on your invoice or contract is the simplest protection.
Not sure what to put on an invoice? Use the invoice generator to create one.
FAQ
How is late payment interest calculated?
The most common method charges interest on the principal by annual rate and days overdue: interest = principal × annual rate ÷ 365 × days overdue. Many contracts also add a fixed late fee.
How much late fee can I charge?
It depends on the late-payment clause in your contract and any local caps on penalties. Without a written agreement you can usually only claim statutory interest — so spell out the rate and fee on your invoice.
Is my data uploaded anywhere?
No. The calculation runs entirely in your browser; nothing is sent to a server.