Invoice Late Fee Calculator
Calculate late fees and interest on an overdue invoice.
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Frequently asked questions
The interest portion uses simple per-annum interest: invoice amount × (annual rate ÷ 100) × (days overdue ÷ 365). Any flat fee you enter is added on top, and the total due is the original invoice plus the late fee.
Both are common. Many net-terms invoices state an annual interest rate on overdue balances, while some businesses prefer a fixed flat fee. This calculator lets you combine them — set either field to zero to use just one.
It depends on your contract and your jurisdiction; some regions cap late-payment interest or set a statutory rate. This tool is an estimate to help you plan, not legal or accounting advice — confirm the allowed rate before billing.
No. The calculation runs entirely in your browser. The invoice amount, rate, and days you type never leave the page and aren't sent to any server.
Last updated 2026-06-23.