Late Fee / Interest Calculator
Calculate the late fee owed on an overdue invoice, based on an annual interest rate applied daily to the outstanding amount.
How It Works
The calculation, explained
Daily rate = annual rate ÷ 365. Late fee = invoice amount × daily rate × days overdue. Many jurisdictions cap the legal maximum late fee rate — confirm your local limit before applying one to a real invoice.
FAQs
Common questions
Is charging a late fee legal?
Generally yes, but maximum allowable rates vary by jurisdiction — check your local regulations, and disclose your late fee policy on the original invoice so it isn’t a surprise.
How do I actually add a late fee to an overdue invoice?
Calculate it here, then add it as an additional line item the next time you re-send or follow up on the invoice. See our overdue invoice follow-up guide.
Beyond The Calculator
Turn this into a real invoice.
Use the full generator to build a proper, line-itemized invoice — free, no signup.