Work out the interest
Four boxes. The sums are shown, so you can check them.
This UK late payment interest calculator shows what you can charge on an overdue invoice: statutory interest of 8% plus the Bank of England base rate, and a fixed sum on top. Enter the amount and the due date. Every step is shown.
| Amount of debt | Fixed sum you can charge (GOV.UK) |
|---|---|
| Up to £999.99 | £40 |
| £1,000 to £9,999.99 | £70 |
| £10,000 or more | £100 |
The rules, from the official pages
Every rule here comes from GOV.UK and the Bank of England. Read on 5 October 2026.
Interest. GOV.UK: Interest on late commercial payments:
When a payment is late. GOV.UK: When a payment becomes late:
The fixed sum. GOV.UK: Claim debt recovery costs on late payments. You can only charge it once for each payment, on top of the interest.
| Amount of debt | What you can charge |
|---|---|
| Up to £999.99 | £40 |
| £1,000 to £9,999.99 | £70 |
| £10,000 or more | £100 |
The base rate. Bank of England: Interest rates and Bank Rate says the current Bank Rate is 3.75%. Bank Rate held at 3.75% on 17 September 2026; the last change took effect on 18 December 2025. Next decision due 5 November 2026. Read 5 October 2026. The Bank's rate history gives the date of each change.
How the sums go. GOV.UK’s worked example: for £1,000 owed and a base rate of 0.5%, the annual interest is £85 (1,000 x 0.085), divided by 365 gives 23p a day, and after 50 days that is £11.50. This page does not round the daily amount first, so the same example comes to £11.64. Rounding at the end is the only difference.
Which base rate. The Late Payment of Commercial Debts (Rate of Interest) (No. 3) Order 2002, article 4, says the rate is 8 per cent a year over the Bank rate in force on the 30 June or the 31 December before the day statutory interest starts to run. GOV.UK says only “8% plus the Bank of England base rate”. The calculator starts with the current rate, as GOV.UK describes it, and shows the Order’s rate for your due date so you can choose.
What this does not cover
- Business-to-business debts in the UK only. It is not for debts owed by a private person who bought for themselves.
- Your contract may set a different rate. GOV.UK says you cannot claim statutory interest if a contract has a different rate of interest.
- One invoice, simple interest, a 365-day year. No part payments, no disputed invoices, no court costs.
- Not legal advice. Check the rules for your case on the official GOV.UK page.
- Nothing you type leaves your browser.
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Now write the reminder
The calculator does the sums. The free Late Payment Chaser adds three reminder emails, friendly, firm and final, with the figures filled in from the same rules.
Late Payment Chaser (UK)
What you give it: The unpaid amount, the invoice date, and the due date if you agreed one.
What you get: What you can claim under UK late-payment law, worked out with a script and shown with official sources, and three reminder emails to send. UK business-to-business debts only. Not legal advice.
Free. It also works as a paste-in text in a chatbot; there the assistant does the arithmetic, so check its working.
How do I calculate late payment interest?
Add 8% to the base rate to get the yearly rate. Multiply the invoice amount by that rate and divide by 365 to get the interest per day, then multiply by the days late. At 11.75% a year, 1,000 pounds earns about 32 pence a day. The calculator shows every step.
Is there a free late payment interest calculator?
Yes. This one is free and runs in your browser, so nothing you type is sent anywhere. It is for UK business to business debts. It can also fill in the GOV.UK worked example so you can check the sums.
What is the statutory late payment interest rate?
GOV.UK says it is 8% plus the Bank of England base rate for business to business transactions. The base rate is 3.75% (since 18 December 2025, read 5 October 2026), so 11.75% a year at today's rate. The 2002 Order fixes the base rate at the one in force on 30 June or 31 December before interest starts, and the calculator shows that rate for your due date.
Can I claim interest on a late payment?
Yes, if the customer is another business, unless your contract sets a different rate. GOV.UK says you can also claim a fixed sum for debt recovery costs. It does not cover a private person who bought for themselves.
Questions people ask
Can I charge interest on a late invoice in the UK?
Yes, if the customer is another business. GOV.UK says you can claim interest and debt recovery costs if another business is late paying for goods or a service. The rate is 8% plus the Bank of England base rate. It does not apply to debts owed by a private person who bought for themselves.
How much is statutory interest on a late invoice?
GOV.UK says statutory interest is 8% plus the Bank of England base rate for business to business transactions. With the base rate at 3.75% that is 11.75% a year. Divide by 365 for the amount per day. The calculator above does the sums and shows them.
When is a business invoice late?
If you agreed a payment date, it is late after that date. If you did not, GOV.UK says the law treats the payment as late 30 days after the customer gets the invoice or you deliver the goods or service, whichever is later. If you agreed a date, GOV.UK says it must usually be within 30 days for public authorities or 60 days for business transactions.
How much can I charge for recovery costs on a late invoice?
GOV.UK lists a fixed sum by size of debt: 40 pounds up to 999.99, 70 pounds from 1,000 to 9,999.99 and 100 pounds from 10,000. You can charge it once for each payment, on top of the interest. You can also claim reasonable costs each time you try to recover the debt.
Which base rate does the calculator use?
The field starts with the Bank of England Bank Rate: 3.75% since 18 December 2025, read on 5 October 2026. You can change it. The Late Payment Order 2002 sets the rate as the base rate on the 30 June or 31 December before interest starts to run. The calculator shows that rate for your due date and lets you switch to it.
Can I add the interest to my invoice?
GOV.UK says to send a new invoice if you decide to add interest to the money you are owed. Check the wording with your own adviser if the sum is large.
What if my contract says something different?
GOV.UK says you cannot claim statutory interest if there is a different rate of interest in a contract. Read your contract first. This tool is for debts that have no such term.
More
Sources
- Check the Bank's page, read 5 October 2026
- GOV.UK: Interest on late commercial payments, read 5 October 2026
- GOV.UK: When a payment becomes late, read 5 October 2026
- GOV.UK: Claim debt recovery costs on late payments, read 5 October 2026
- Bank's rate history, read 5 October 2026
- The Late Payment of Commercial Debts (Rate of Interest) (No. 3) Order 2002, read 5 October 2026