Pricing & Profit calculator
Invoice Late Fee Calculator
Work out a simple late fee amount and total amount due on an overdue invoice using a one-off fee or an annualised simple-rate method.
Why use it
- Useful for checking the dollar impact of a late fee before updating an overdue invoice balance.
- This tool is only a calculation aid. It does not confirm whether a late fee is enforceable or commercially appropriate in your situation.
- The annualised option uses a simple-rate method based on days overdue, not compound interest.
Calculator tool
Use the invoice late fee calculator
Work out a simple late fee amount and total amount due on an overdue invoice using a one-off fee or an annualised simple-rate method.
Share this result
Email it to yourself, send it to a customer, or copy the figures into a quote — all without an account.
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“Email this” opens your own email app (Gmail, Outlook, Apple Mail) with the figures and a link back already filled in. Nothing is sent through BizTools.au.
Important note
BizTools.au is designed to make business numbers easier to check, but calculator outputs still need judgment and real-world context.
- Calculator results are general estimates only and depend on the figures entered.
- Examples and summaries are provided for general information, not legal, tax, accounting, payroll, or financial advice.
- Before relying on a result for a real decision, check your assumptions and get qualified advice where needed.
How it works
Understand the formula before you use the result
The calculator uses a simple working formula so you can sense-check the result quickly and explain it clearly inside your business.
Invoice late fee formula
One-off late fee = invoice amount × late fee rate
Annualised simple late fee = invoice amount × late fee rate × (days overdue ÷ 365)
Total amount due = invoice amount + late fee amount
The annualised method uses a simple proportion of the yearly rate. It does not compound the fee.
Worked example
See the numbers in a realistic scenario
Use the example below as a sense check when you compare the calculator result to a real quote, sale, or pricing decision.
Worked example
Worked example: applying a simple annualised late fee
A $2,500 invoice is 30 days overdue and the business wants to test a 10% annualised simple late fee.
- Invoice amount: $2,500
- Late fee rate: 10%
- Days overdue: 30
- Fee method: Annualised simple rate
Calculation steps
- Late fee = $2,500 × 10% × (30 ÷ 365) = $20.55
- Total amount due = $2,500 + $20.55 = $2,520.55
At a simple 10% annualised rate over 30 days, the late fee comes to about $20.55.
FAQ
Common questions about the invoice late fee calculator
These are the practical questions operators usually run into when they apply the result to a real business decision.
What is the difference between one-off and annualised?
A one-off fee applies the percentage once to the invoice amount. An annualised simple rate scales the percentage by how many days the invoice is overdue.
Does this calculator check whether I can legally charge the fee?
No. It only helps with the arithmetic. Whether a fee is enforceable depends on your terms, contract wording, and the circumstances of the debt.
Does the annualised method compound over time?
No. This tool uses a simple-rate calculation only. It does not add compounding or interest-on-interest.
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