Estimate overdue charges from the invoice balance, lateness, and the clause in your terms.
Total Late Fees
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Enter invoice amount, days late, flat fee, interest rate, and interest mode to estimate the new balance due.
Tap an example to prefill the calculator with sample values.
Freelance invoice at 45 days
$5,000 invoice with a flat fee and daily interest
A common late-payment clause structure used in service agreements and invoice terms.
Result: The late fee can move from symbolic to meaningful once interest keeps accruing beyond the first month.
Small retainer overdue
Monthly interest on a lower-dollar invoice
Useful for recurring retainers or small-business invoices where the clause is written in monthly terms rather than daily terms.
Result: Monthly simple interest is easier to explain to clients, though the economic effect can still add up.
Larger B2B invoice
Higher balance with no flat fee
A cleaner interest-only clause where the size of the invoice matters more than the administrative fee.
Result: On bigger invoices, even a moderate annual rate can create meaningful carry cost quickly.