Estimate overdue invoice fees
Use the late fee calculator as a worksheet for unpaid invoices when your agreement includes late payment terms. Enter the invoice amount, due date, payment date, and fee method to estimate a possible charge.
Free tool
Late Fee Calculator
Estimate an overdue invoice late fee from the invoice amount, due date, grace period, and fee terms. Use it as a worksheet, not legal advice.
Monthly, annual, or flat fee · Copyable summary · No invoice data uploaded
Inputs
Estimate a common late fee
Result
Late fee estimate
Use this as a billing worksheet. Laws and contract terms vary, so confirm any late fee before adding it to an invoice.
Days overdue
0
Late fee
$0.00
Estimated total
$2,370.00
Suggested wording
According to the payment terms on invoice, the balance is 0 days overdue. The estimated late fee is $0.00, bringing the estimated total due to $2,370.00.
Monthly, annual, and flat fees
Some agreements use a monthly percentage, some use an annual rate, and some use a flat fee. The calculator keeps these methods separate so the math is easier to review.
Using late fee estimates carefully
Late fees should usually be based on agreed payment terms. Confirm that the fee is allowed before adding it to an invoice, statement, or reminder email.
Pair the estimate with clear wording
When you follow up, show the original invoice amount, days overdue, fee method, and total separately. Clear detail makes the reminder easier to review and helps avoid turning a payment delay into a dispute.
FAQ
How are late fees calculated?
You can estimate monthly, annual, or flat late fees based on the invoice amount, due date, and grace period you enter.
Are these late fees legally enforceable?
Late fee rules vary by contract, state, and country. This calculator is for planning only and is not legal advice.
Do I need to create an account?
No. The calculator runs in your browser.