Home › Free tools › Late payment interest calculator

Late payment interest calculator

When a business pays your invoice late, the law lets you charge interest and a fixed sum for the hassle. Work out exactly what you can claim. Nothing you type leaves your device.

Based on GOV.UK guidance, last checked 29 October 2026 · A guide only, not legal advice

Invoice amount Including VAT, if you charged it

£

Date payment was due The date in your agreed payment terms. If you didn’t agree any, it’s 30 days after the customer got your invoice (or the goods, if later)

Date paid, or today if not paid yet

Bank of England base rate 3.75% for debts that became late between 1 July and 31 December 2026 (the rate on 30 June 2026). For other periods, use the rate on the 30 June or 31 December before

Work out what I can claim

How statutory late payment interest works

• You can charge interest at 8% plus the Bank of England base rate. It’s simple interest worked out for each day late.
• Use the base rate on 30 June for debts that become late from 1 July to 31 December, and the rate on 31 December for debts that become late from 1 January to 30 June.
• You can also claim a fixed amount for each late invoice: £40 for debts under £1,000, £70 for £1,000 to £9,999.99 and £100 for £10,000 or more.
• It only applies to business-to-business sales. If your contract sets a different late payment rate, that rate applies instead.

Example from GOV.UK: a £1,000 debt at 8.5% is £85 interest a year, which is 23p a day. Your customer would also owe £70 fixed compensation.

Source: Late commercial payments: charging interest and debt recovery on GOV.UK.