Tools
Late payment & late fee calculator for overdue invoices (2026)
Enter the open invoice amount and how many days it is late. Estimate a late fee percent or simple interest on late payment, then follow up with a reminder email. Due date calculator · Reminder templates
Updated May 22, 2026
Calculator
Not sure? Use the due date calculator.
One-time percent of the open invoice balance (check your contract).
Open balance
$2,400.00
Late charge
$36.00
Total if fee applies
$2,436.00
Estimated late fee: $36.00
1.5% of $2,400.00 on an invoice 14 days past due. Confirm your contract before invoicing a late fee.
Ready to follow up? Invoice reminder templates or start a free trial to automate sends.
Late fee vs interest on late payment
A late fee is often a fixed percent of the invoice written in your terms. Interest on late payment usually uses an annual rate applied to the days the balance was overdue.
This calculator is for freelancer and studio client invoices, not tax or IRS penalties. Always match what your contract and local rules allow before charging a client.
Late payment calculator FAQ
- What is a late payment calculator?
- It estimates the cost of an overdue client invoice: either a late fee as a percent of the balance or simple interest from an annual rate. Use it to decide how firmly to follow up, not as legal advice.
- How is a late fee calculator different from interest?
- A late fee is often charged once as a percent of the invoice. Interest accrues over time based on an annual rate and the number of days late. This tool supports both methods.
- How do you calculate interest on a late payment?
- A common approach is simple interest: invoice balance × (annual rate ÷ 100) × (days late ÷ 365). Enter your rate and days late above.
- Should I charge a late fee or only send a reminder?
- Many businesses send polite reminders first. If terms allow a late fee, say so clearly in the email. NowPaid helps you automate reminder emails in your tone.