KitebillUK late payment interest calculator
A UK business paid your invoice late, or still hasn’t paid? Work out the statutory interest you can claim (8% a year plus the Bank of England Bank Rate), the fixed sum for the cost of chasing it, and get the lines for an interest invoice and a paragraph for your email. Nothing you type leaves your browser.
You can claim - on top of the invoice: - in all.
Interest invoice lines (gov.uk says to send a new invoice for the interest):
Make the interest invoice opens the free invoice generator in pounds with these two lines. The details travel in the part of the link after #, which browsers don’t send to any server.
How UK statutory interest works
- Who can claim: a business owed money by another business (or a public body) for goods or services. It doesn’t apply to sales to consumers, and you can’t claim it if your contract sets a different interest rate (gov.uk: interest on late commercial payments).
- When it’s late: the day after the agreed payment date. With no agreed date, 30 days after the customer gets the invoice or you deliver, whichever is later (gov.uk: when a payment becomes late).
- The rate: 8% a year over the Bank of England’s rate in force on 30 June (for interest that starts to run from 1 July to 31 December) or 31 December (for 1 January to 30 June), immediately before interest starts to run (The Late Payment of Commercial Debts (Rate of Interest) (No. 3) Order 2002, article 4). Bank Rate was 3.75% on both 31 December 2025 and 30 June 2026 (Bank of England Bank Rate history, checked 20 October 2026), so a debt that became late in 2026 carries 11.75% a year.
- The maths: simple interest per day: amount × rate ÷ 365 × days late. gov.uk’s own example (£1,000 at 8.5% for 50 days) rounds the daily figure to 23p first and gets £11.50; this calculator only rounds the final amount, so it shows £11.64 for the same numbers (type 0.5 in "Bank Rate" to see it).
- The fixed sum: £40 for a debt up to £999.99, £70 from £1,000 to £9,999.99, £100 for £10,000 or more, once per late payment. You can also claim reasonable costs of recovering the debt beyond that (gov.uk: claim debt recovery costs).
Before you claim
Statutory interest is a legal right, but whether to use it is a business decision: a polite reminder often gets the money in faster than an interest claim, and some clients will be offended by one. Many freelancers mention it on the invoice in advance ("We will charge interest and a fixed sum on late payments under the Late Payment of Commercial Debts (Interest) Act 1998") and only claim it from clients who keep paying late. The free payment reminder email generator writes the reminder first.
Outside the UK? This calculator covers the UK Act only. It applies to contracts governed by the law of a part of the UK, so if you are billing a UK business from abroad, whether you can use it depends on which law your contract is under. EU countries have similar rules from the Late Payment Directive (2011/7/EU), with their own rates. For a late fee your client agreed to in your contract, use the late fee calculator instead.
This page does arithmetic from the published rules. It is not legal advice; if a large sum is at stake, talk to a solicitor or Citizens Advice.
Stop invoices slipping in the first place
The free Kitebill app marks sent invoices as overdue the day after they’re due and lists who owes what, so you see a late payment on day one instead of day fifty. It doesn’t work out statutory interest for you; use this page for that. Your data stays in your browser; 3 clients and 10 invoices are free, and Pro is US$29 once.
More free tools
Questions
How much interest can I charge on a late invoice in the UK?
If your contract doesn’t set its own rate, you can claim statutory interest at 8% a year plus the Bank of England Bank Rate on a late business-to-business payment. The Bank Rate used is the one in force on 30 June or 31 December before the payment became late, and it stays fixed for that debt. For a debt that became late in 2026 that is 8% + 3.75% = 11.75% a year.
How is statutory late payment interest calculated?
Multiply the amount owed by the yearly rate, divide by 365 to get the daily interest, and multiply by the number of days late. For example, £1,000 at 11.75% is £117.50 a year or about 32p a day, so 50 days late is £16.10. It is simple interest: it doesn’t compound.
What is the fixed sum for late payment?
On top of interest you can claim one fixed sum per late invoice towards the cost of recovering it: £40 for a debt up to £999.99, £70 from £1,000 to £9,999.99 and £100 for £10,000 or more. You can also claim reasonable recovery costs above that if you actually incurred them.
When does a payment become late?
On the day after the agreed payment date. If no date was agreed, the law says payment is late 30 days after the customer gets the invoice, or 30 days after you deliver the goods or service if that is later.
Can I charge statutory interest to a private individual?
No. The Late Payment of Commercial Debts (Interest) Act 1998 only covers payments between businesses (including public bodies) acting in the course of business. It doesn’t apply to consumers, and you can’t claim it if your contract already sets a different interest rate.
Does this tool save my numbers?
No. Everything is calculated in your browser; nothing is stored or uploaded, and the page makes no requests to other sites.