Free tool · UK business-to-business invoices
Late payment interest calculator
Owed money by another business? Enter the invoice and this works out the statutory interest (8% plus the Bank of England base rate), the fixed sum you can add, and the total owed today, with every line of the working shown. It runs in your browser and nothing you type is sent anywhere.
Enter the amount and dates above to see what you can claim.
Ready-to-send interest invoice
GOV.UK says to send a new invoice if you decide to add interest. Copy this into it, or into your chase email.
Still not paid?
The UK Ltd Invoice Chase Swipe File gives you the exact words for every stage: the friendly reminder, the final notice that adds interest and the fixed sum, the letter before action, and the phone script for the accounts team. Printable, fill in the gaps, send today.
Get the Chase Swipe File · £14.99 Free letter before action formKeep on top of who owes you with the Small Business Bookkeeping Sheets UK.
How the figures are worked out
When it is late. If you agreed a payment date, the invoice is late from the next day. If you did not, the law says it is late 30 days after the customer gets the invoice, or 30 days after you deliver, if that is later. Agreed terms are usually up to 60 days between businesses and up to 30 days for public authorities.
Interest. Statutory interest is 8% a year plus the Bank of England base rate. The base rate used is the one in force on 30 June or 31 December immediately before the invoice became late, and it stays the same for that debt even if the Bank changes the rate later. Daily interest is the yearly figure divided by 365. This calculator rounds to the penny only at the end, so it can be a few pence higher than the GOV.UK worked example, which rounds the daily figure first.
Fixed sum. Once per invoice you can add £40 for a debt up to £999.99, £70 for £1,000 to £9,999.99, and £100 for £10,000 or more.
When it does not apply. Not for private customers, and not if your contract sets its own interest rate (use that instead).
Figures from the Late Payment of Commercial Debts (Interest) Act 1998 as set out on GOV.UK, and the Bank of England Bank Rate history (table last checked ). This is general information, not legal advice. For a disputed debt, an insolvent customer or a claim over the small claims limit, get advice.