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Invoice Late Fee Calculator

Calculate the late fee on an overdue invoice from a monthly interest rate and the number of days overdue.

Late fee
45$
Total amount due
$2045

Formula: Fee = amount × monthly rate% × days ÷ 30

About Invoice Late Fee Calculator

Invoice Late Fee Calculator is a free online calculator that gives you an instant, accurate result as you type. Calculate the late fee on an overdue invoice from a monthly interest rate and the number of days overdue.

The calculation uses the standard formula Fee = amount × monthly rate% × days ÷ 30 and updates live with every change to the inputs. Everything runs client-side in your browser — fast, private, and free to use as often as you like.

A late fee of 1.5% per month (18% per year) is a common standard on business invoices, though maximum allowable rates vary by jurisdiction.

Frequently Asked Questions

Is Invoice Late Fee Calculator free to use?

Yes. Invoice Late Fee Calculator is completely free, with no sign-up, no downloads, and no usage limits. You can use it as many times as you like on any device with a web browser.

How accurate is this calculator?

The calculator applies the standard formula (Fee = amount × monthly rate% × days ÷ 30) with full floating-point precision and rounds only the displayed result. For most practical purposes the results are exact.