Free Calculator

Late Fee Calculator

Calculate the exact late fee or interest charge on an overdue invoice. Supports both simple and compound interest methods.

Calculate your late fee

Interest Type

Interest accrues only on the original principal for each day overdue.

Late fee$9.86
Total amount due$1,009.86

Formula: Principal × Rate × Days ÷ 365

Email me this result

We only use your email to send this result.

How Late Fee Calculation Works

Three steps to estimate what you can charge on overdue invoices.

1

Enter invoice details

Input the original invoice amount, the annual interest rate you charge, and how many days the payment is overdue.

2

Choose interest type

Select simple interest for a straightforward calculation, or compound interest if your terms specify monthly compounding.

3

Get your results

See the late fee and total due instantly. Use these figures when following up with your client.

Frequently Asked Questions

Common questions about late fees and interest charges on invoices.

Next step

Send the next invoice before it is late

Late fees are the remedy. Clear terms and an invoice that can be paid online are the prevention. Make one now, download the PDF or save it into a new account.

Make an invoice now

Start with the details that belong on your invoice.

12 × $15.00$180.00

Current total

$180.00

Open the full builder

No signup, no card. Everything happens in your browser.

Invoice preview

This is what your client sees.

Live

Green Acre Landscaping

INVOICE

INV-202609-001

Issued

Sep 25, 2026

Due

Oct 25, 2026

Currency

USD

From

Green Acre Landscaping

Bill to

Riverside Cafe

DescriptionQtyRateAmount
Lawn maintenance, June12$15.00$180.00
Subtotal$180.00
Total due$180.00

Payment due within 30 days. Thank you for your business.

Live preview, updates as you type

Automate Late Fee Tracking

Stop calculating late fees manually. Invoice My Clients automatically tracks overdue invoices and calculates interest charges for you.

Related resources

Learn more about interest on invoices and overdue payment workflows.