Late payment interest calculator
When a business customer pays you late, UK law lets you charge statutory interest plus a fixed compensation sum, with no contract clause needed. Enter the invoice and dates to estimate what you are owed on top.
How it works
For late commercial (business-to-business) payments, you can charge statutory interest of 8% plus the Bank of England base rate, calculated daily from the day the debt became late. On top of the interest you can also claim a one-off fixed compensation sum per late invoice: £40 for debts under £1,000, £70 for £1,000 to £9,999.99, and £100 for £10,000 or more.
A debt becomes late on your agreed payment date, or (if none was agreed) 30 days after the customer receives the invoice or the goods or service, whichever is later.
How to use the result
The fastest way to use this is in your payment reminder: state the amount, the days overdue, the statutory interest accruing and the fixed sum you are entitled to. Many customers pay promptly once they see the figure is real and rising. You are not obliged to charge it, but the right exists whether or not it is written into your contract, unless your contract sets its own substantial remedy.
Statutory interest is 8% + the Bank of England base rate (3.75% as of June 2026, giving 11.75%). The base rate is reviewed regularly - the next decision was due 18 June 2026 - so check the current rate before relying on a figure, and note the statutory rate is fixed in six-month periods (set on 31 December and 30 June). This is an estimate, not legal advice. Figures verified June 2026 from GOV.UK and the Bank of England.