Late payment fee calculator
Enter the overdue amount, the late fee, the annual rate and the days late to see how much the delay adds to what you pay.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter overdue amount, flat late fee, annual late interest rate and days late.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Late interest = amount × annual rate ÷ 365 × days late. Cost = flat fee + late interest. Annualised cost = (cost ÷ amount) × 365 ÷ days.
Example
Inputs: Overdue amount = 5,000, Flat late fee = 50, Annual late interest rate = 12 % a year, Days late = 30 days. Result: Cost of paying late: 99.32; Late interest: 49.32; Cost as a share of the amount: 1.99%.
Limits and caveats
- Assumes simple daily interest on a 365-day year; contracts may charge monthly or differently.
- In many Islamic contracts late charges go to charity rather than the financier, but they are still a cost to you.
Questions about this tool
Why is the annualised cost high when the fee is small?
A flat fee charged for a few days looks much bigger once it is turned into a yearly rate.
Can I leave the rate at zero?
Yes. If the penalty is only a flat fee, set the rate to zero.
Does paying late affect my credit record?
Late payments can be reported to credit bureaus, an effect this tool does not measure.