Calculate interest and fees on late invoices, the total amount due, and what delayed payment really costs your business.
Overview
The Invoice Late Payment Calculator computes interest and fees on overdue invoices, the total amount owed, and the effective annual cost of a delay. It helps freelancers, consultants, and small businesses set payment terms, charge consistent late fees, and quantify what late-paying clients really cost.
Common Use Cases
Late fee calculation
Payment terms planning
Accounts receivable review
Client payment follow-up
Interest calculation on overdue invoices
Net-30 and Net-60 term analysis
Freelance invoicing
Collection process improvement
Cash flow planning
B2B invoice management
Contract term negotiation
Aging receivables analysis
How to Use
1
Enter the original invoice amount.
2
Input how many days the payment is late.
3
Set the annual interest rate to apply.
4
Optionally add a flat late fee.
5
Review the interest charged, total late fee, and total amount due.
6
Check the effective annual rate for context on your payment terms.
Example Scenario
Overdue Client Invoice
A freelancer has a client invoice that is 30 days overdue. The calculator determines the interest and fee to add and shows what the delay is worth in annualized terms.
Technical Notes
Interest is calculated as the invoice amount times the annual rate times the fraction of the year the payment is late.
A flat fee can be added to cover administrative costs of chasing overdue payments.
Total late fee combines the accrued interest and any flat fee.
Total due is the original invoice plus the total late fee.
The effective annual rate annualizes the total fee, showing the true cost of the delay.
Common Mistakes
Not stating late fees in terms up front
Using monthly rates as if they were annual
Forgetting to include a flat administrative fee
Charging interest on top of compounded fees
Ignoring grace days in the contract
Never following up on overdue invoices
Frequently Asked Questions
Use a rate stated in your payment terms, commonly 1-2% per month (12-24% annually), or the statutory rate allowed in your jurisdiction.
After the invoice due date plus any grace period defined in your terms, typically Net-30 or Net-60 from the invoice date.
Yes. It shows the annualized cost of the delay and helps you decide whether your late-fee policy is strong enough to deter slow payers.
Yes, many businesses charge interest plus a flat administrative fee, as long as the terms are disclosed in advance.