Late Fee on a $500 Invoice 15 Days Overdue
Calculate the late fee on a small $500 invoice that is 15 days past its due date at 18% annual interest.
How to use this tool
- Enter the unpaid invoice amount.
- Enter the annual interest rate from your payment terms (e.g. 18%).
- Enter how many days the invoice is past due.
- Add a flat fee if your terms include one, then read the total due.
Even small invoices can accumulate late fees — this calculator shows the exact total due on a $500 invoice that is 15 days overdue.
Frequently asked questions
- What late fee can I legally charge?
- It depends on your contract and local law. Common freelance terms are 1.5% per month (18% per year), but some jurisdictions cap late-payment or interest rates, so confirm the figure you enter is enforceable where you operate.
- Is the interest simple or compounding?
- This calculator uses simple daily interest on the original invoice, which matches how most freelance terms are written. It does not compound the accrued interest into the balance.
- Why divide the annual rate by 365?
- To turn an annual percentage into a daily one. Multiplying the daily rate by the invoice gives interest per day, and by the days overdue gives the total interest charge.