Late Payment Interest Calculator
Work out how much interest an overdue invoice has accrued, and what the new total should be.
How this calculator works
Everything runs in this browser tab: the amount, dates, and rate you enter are never sent anywhere. This tool only does arithmetic on the rate you choose. It never picks a rate for you or gives tax or legal advice.
Related tools
Next step
Take it further, in a spreadsheet
These tools run in your browser and keep nothing. When you'd rather have the same thing as a file you own, there are two spreadsheets, depending on how much you want to track.
Start here: one invoice
The Free Invoice Template builds one invoice in Excel or Sheets: fill in your details once, get a print-ready invoice with its own totals. No macros, one email address.
Get the free template →When there's more than one invoice to track
The Small Business Finance Kit is one Excel workbook that tracks every invoice, flags who's overdue, logs expenses, and calculates your profit automatically. Seven tabs, one file, no subscription.
Get the Small Business Finance Kit →