Invoice Late Fee Calculator
Compute late fees and updated total from invoice amount, late days, and flat/percent/daily penalty terms.
Last reviewed by the Radiatus Cloud team
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Work out the late fee on an overdue invoice
When an invoice is paid later than its due date, a late fee may apply, either as a flat charge or as a percentage that accrues over time. This calculator computes the correct late fee and the updated total from the invoice amount, the number of days overdue, and your own flat or percentage-based terms, so the figure you bill is accurate and consistent.
Why clear late terms matter
A late fee only genuinely works, and holds up if a client questions it, when it is calculated consistently with the terms you actually stated on the invoice, and there are two common models to choose between. One is a flat fee charged per overdue period; the other is a percentage of the outstanding amount that accrues with the number of days late. Getting the calculation exactly right keeps your invoicing professional and defensible, and it hands the client a clear, correct figure rather than an arbitrary one. Seeing the updated total also makes the real cost of delay visible, which can quietly encourage prompter payment next time.
A correct, defensible figure
The calculation runs entirely in your browser, so your figures are never uploaded and stay on your own machine, which matters for anything involving money and personal finances.
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Frequently Asked Questions
How is a late fee calculated?
Either as a flat charge per overdue period, or as a percentage of the outstanding amount accruing over the days late. The calculator supports both.
Which late fee model should I use?
Whichever your invoice terms state. A flat fee is simple; a percentage scales with the amount and delay. Consistency with your terms is what matters.
Why compute it precisely?
Because a consistent, correct figure keeps your invoicing professional and defensible, rather than an arbitrary charge a client might dispute.
Does it show the updated total?
Yes. It adds the late fee to the invoice amount so you can see and bill the correct overdue total.
Is my data uploaded?
No. The calculation runs entirely in your browser.
Privacy & Security
Calculated locally in your browser. Check your contract terms and local laws.
How to Use
Enter invoice amount and late fee terms to calculate fees and total due.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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