Late Fee Calculator
Calculate the exact late fee or interest charge on an overdue invoice. Supports both simple and compound interest methods.
Calculate your late fee
Interest accrues only on the original principal for each day overdue.
Formula: Principal × Rate × Days ÷ 365
How Late Fee Calculation Works
Three steps to estimate what you can charge on overdue invoices.
Enter invoice details
Input the original invoice amount, the annual interest rate you charge, and how many days the payment is overdue.
Choose interest type
Select simple interest for a straightforward calculation, or compound interest if your terms specify monthly compounding.
Get your results
See the late fee and total due instantly. Use these figures when following up with your client.
Frequently Asked Questions
Common questions about late fees and interest charges on invoices.
Automate Late Fee Tracking
Stop calculating late fees manually. Invoice My Clients automatically tracks overdue invoices and calculates interest charges for you.
Related resources
Learn more about interest on invoices and overdue payment workflows.