How much is a late invoice worth now?

Add interest and a flat fee to an overdue invoice and see the total you can ask for.

Total now due

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Days overdue: —
Original invoice: —
Interest so far: —
Flat late fee: —
Interest per day: —

Invoice amount

Due date Calculate as of

Interest per year

18% a year is 1.5% a month. Flat late fee

How the total is calculated

Simple interest: amount × yearly rate ÷ 365 × days overdue, plus any flat fee once the invoice is past due.

Can I charge any rate I want?

Not necessarily. Many places cap late fees or interest, and a charge normally needs to be in your contract or invoice terms before the work starts. Check your local rules or ask a lawyer. This tool only does the arithmetic.