Late Payment Interest Calculator
Enter the invoice amount, your late fee rate, and how many days overdue it is to calculate the interest owed.
Interest owed$0.00
Total amount due$0.00
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Frequently asked questions
Q.Can I actually charge interest on a late invoice?
In most places, yes — as long as your original contract or invoice terms disclosed the late fee rate before the sale. Charging it retroactively without having stated it upfront is generally not enforceable, so check your invoice terms and local law.
Q.What's a reasonable late fee rate?
1-1.5% per month (12-18% annually) is common practice for small business invoices, though some jurisdictions cap the maximum rate you can charge. Check your local regulations before setting a rate.