Invoice Late Payment Calculator
Estimate how overdue an invoice is, calculate a simple late fee estimate, and generate a polite follow-up payment message you can copy and send. Built for Australian small businesses that want a clearer and more practical way to chase overdue invoices.
This invoice late payment calculator helps Australian small businesses estimate overdue invoice days, calculate a simple late fee, and create a professional payment reminder message. If you are dealing with late-paying clients, this tool gives you a quick way to understand the impact on your cash flow.
Late Payment Estimator
Enter the invoice details below to estimate overdue days, a suggested late fee, and the total suggested amount.
Results
What this calculator helps with
This is useful when you want a quick sense of how overdue an invoice is and a cleaner way to follow up without sounding overly aggressive.
- See the number of days an invoice is overdue
- Estimate a simple late fee based on a monthly rate
- Generate a polite follow-up message you can copy and send
- Get more organised with overdue receivables and cash flow
How to use this calculator
- Enter your business name and your client’s name.
- Add the invoice amount and the monthly late fee rate you want to estimate from.
- Select the invoice due date and the current date.
- Click calculate to view overdue days, suggested late fee, and the message output.
This tool is designed to keep things simple. It is best used as a practical estimate and a communication aid, not as a substitute for your formal payment terms or legal advice.
What to keep in mind with late payments
A late fee estimate can be useful for internal tracking or discussing overdue accounts, but what you can actually charge depends on your agreement with the client and the terms already set out in your invoice or engagement terms.
- Make sure your payment terms are clear before the invoice becomes overdue
- Keep your reminder messages professional and direct
- Track overdue invoices regularly instead of reacting too late
- Use the same approach consistently across clients where appropriate
Related help for small businesses
If overdue invoices are part of a bigger cash flow issue, these pages may be useful as well:
Frequently asked questions
Can I legally charge a late fee on an invoice?
That depends on your agreement, payment terms, and the circumstances. This calculator is a simple estimate tool only and does not determine what is legally enforceable.
How is the late fee estimated here?
This page uses a simple monthly percentage rate converted into a daily estimate, then applies it to the number of days overdue.
Who is this calculator for?
It is useful for Australian small business owners who want a quick estimate and a more polished way to follow up on overdue invoices.
Can I use the generated message as-is?
You can use it as a starting point, but it is worth checking that it matches your invoice terms, tone, and client relationship before sending.
How do I calculate a late fee on an invoice in Australia?
A common approach is to apply a monthly percentage rate to the invoice amount and convert it into a daily rate based on how many days the invoice is overdue. However, the actual amount you can charge depends on your agreed payment terms.