Invoice Late Fee Calculator

Work out a late fee or interest charge on an overdue invoice.

How late fees on invoices work

Late payment is one of the biggest headaches of freelancing. A clear late fee, written into your contract and printed on every invoice, gives clients a reason to pay on time. The two common approaches are a percentage interest charge, usually quoted per month, and a one-off flat fee. Some businesses use both.

This calculator applies the monthly rate day by day, so a payment 45 days late is charged for exactly 45 days rather than a full two months. That is the fairest method and the easiest to explain to a client.

The formula

Daily rate = monthly rate × 12 ÷ 365
Interest = invoice amount × daily rate × days overdue
Total due = invoice amount + interest + flat fee

Worked example

A $2,000 invoice is 45 days late and your terms say 1.5% per month. That is 18% a year, or about 0.0493% a day. $2,000 × 0.000493 × 45 ≈ $44.38 of interest, so the client now owes $2,044.38.

Before you charge a late fee

• Put it in writing first. A late fee is easiest to enforce when it was in the contract or on the invoice before the work began.
• Check local rules. Many states and countries cap the interest you may charge or set a statutory rate. Confirm what applies to you.
• Send a friendly reminder a few days before and after the due date. Most late payments are simply forgotten.

Frequently asked questions

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