UK Late Payment Interest Calculator
Work out the statutory interest and fixed fee you can charge on a late business invoice.
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How to do it
- 1Fill in the boxes
Type your numbers or pick the options you need.
- 2See the result
The answer updates right away as you change a value.
- 3Use it
Copy the result or note it down. Nothing is sent anywhere.
About this tool
Enter the invoice amount, the days it is overdue and the Bank of England base rate. Under the Late Payment Act you can claim 8 percent above base rate a year plus a fixed fee of £40, £70 or £100. Rates and thresholds are for the 2026-27 tax year and can change. A guide only, check gov.uk for the official figures.
The rules
Businesses can charge statutory interest on a late invoice to another business. The rate is 8 percent over the base rate at the time. You can also claim fixed compensation of £40 for debts under £1,000, £70 for £1,000 to £9,999.99 and £100 for £10,000 or more.
Example
A £5,000 invoice that is 30 days late at a base rate of 4 percent adds about £49 of interest and a £70 fee.
Tips
State your late payment terms on invoices. Send a polite reminder first. These rules cover business to business supply, not consumers.
Frequently asked questions
Does this apply to consumers?
No. The Late Payment of Commercial Debts Act covers business to business payments.
Which base rate should I use?
The Bank of England rate in force on the date the debt became overdue. The tool uses the figure you type.
Can I charge more?
Contract terms can set a different rate if it is a substantial remedy.
Is the fee per invoice?
Yes, a fixed fee applies for each late invoice.