Small overdue invoice
Invoice is $8,500, fee rate is 1.5% per month, and payment is 18 days late.
Late fee is about $76.50.
The fee scales with time, so shorter delays create smaller charges.
Late Payment Fee Calculator
Use this calculator when you need a quick late-fee estimate for an overdue invoice and want the total due to stay clear.
Inputs
Late Payment Fee Calculator
Estimate the fee added when an invoice is paid after the due date.
Results
Late fee snapshot
The fee is prorated by the number of days the payment is late.
Late fee
$76.50
Extra fee charged for the delay.
Total due
$8,576.50
Invoice amount plus the fee.
Effective rate
0.90%
Actual fee as a share of the invoice.
Quick take
A quick read before you calculate
Use this calculator when you need a quick late-fee estimate for an overdue invoice and want the total due to stay clear.
Formula
Late fee formula
Examples
2-3 real scenarios to make the result easier to trust.
FAQ
Clear answers to the questions people usually ask first.
Formula
Late fee formula
Late fee = Invoice amount × Monthly fee rate × (Days late ÷ 30). Total due = Invoice amount + Late fee.
The fee is prorated by days late, so a partial month only charges part of the monthly rate.
Examples
Large unpaid bill
Invoice is $20,000 at 2% per month and 30 days late.
Late fee is $400.
A full month at a higher rate can add up quickly.
Short delay
Invoice is $3,000 at 1% per month and 6 days late.
Late fee is about $6.
This helps keep the penalty fair when a payment is only slightly overdue.
When to use
Use it when you send payment reminders, calculate overdue charges, or update a client before the balance keeps growing.
Common mistakes
- Charging a full monthly fee when the invoice is only late for a few days.
- Forgetting to add the late fee to the original invoice amount.
- Using a fee policy that does not match your contract terms.
FAQ
Is this a legal fee calculator?
No. It only estimates the amount based on your chosen rate and timing. Always follow your local rules and contract terms.
Can I change the fee policy later?
Yes. If your late-fee terms change, update the rate and rerun the calculation.
Next step
Need cleaner collections?
QuickBooks or Xero can help if you want overdue invoices, reminders, and payments in one place.
Use the calculator again whenever the invoice amount or delay changes.