Late Payment Fee Calculator
Charging a late fee is common, but it only works if it is stated in advance and the amount is clear. This calculator shows what an overdue invoice has grown to under a monthly percentage, an annual rate or a flat fee, so you can set the policy and write the reminder with exact numbers.
Enter your numbers to see the result.
How this calculator works
- Enter the invoice amount and how many days it is overdue.
- Enter the monthly late fee percentage from your terms. 1 to 1.5 percent per month is a common figure on invoices.
- Add a flat fee if your terms include one.
- Read the total now due and use the numbers in your reminder or follow-up invoice.
The formula
Percentage fee = invoice amount x monthly rate x (days overdue / 30). Total due = invoice amount + percentage fee + flat fee. This uses simple, not compound, interest.
Example: a $2,500 invoice, 45 days overdue, at 1.5% per month. Fee = 2,500 x 0.015 x 1.5 = $56.25. Total due = $2,556.25.
Frequently asked questions
Can I charge a late fee on an invoice?
Generally yes if the fee was agreed in a contract or stated on the invoice before the work was done. Some states cap interest rates or late fees, so check the rules where you operate. This is not legal advice.
What is a typical late fee?
Many businesses use 1 to 1.5 percent per month, sometimes with a small flat fee. Your agreement and local law decide what is allowed.
Should I state the late fee on the invoice?
Yes. Put the percentage and the due date in the invoice notes, for example "1.5% per month on overdue balances", so there is no surprise later.
Simple or compound interest?
This calculator uses simple interest, which is what most invoice terms describe. Compound interest must be explicitly agreed.
Estimates for planning only, not financial, tax or legal advice. Nothing you enter leaves your browser.