Late payment interest calculator

Work out the statutory interest and fixed compensation you can claim when a business pays your invoice late, with the rate and every step shown.

For UK business to business invoices only, under the Late Payment of Commercial Debts (Interest) Act 1998.

The invoice

Amount owed The invoice total, including any VAT.

Invoice number Optional, for the claim message

Payment was due

Date paid

The payment date you agreed. Never agreed one? It is 30 days after they got your invoice or the work was done, whichever is later.

Still not paid? Leave the date paid as today. Interest keeps adding up each day until they pay.

The rate

My contract sets its own interest rateThen that rate applies instead of statutory interest, and the fixed compensation does not.

The working

Example

£1,000 due on 30 June 2026 and paid on 19 August 2026. Type your own figures to replace it.

You can claim£86.10

Days late50

The rate

Bank Rate on 30 June 2026: 3.75%
Plus the statutory 8%: 8%
Statutory rate: 11.75% a year

Interest starts the day after the due date: 1 July 2026. For interest that starts between 1 July and 31 December, the Bank Rate on 30 June applies, and that rate stays with the debt until it is paid.

The interest

Days late 1 Jul 2026 to 19 Aug 2026: 50
Interest per day: £0.32
Interest: £16.10

£1,000.00 × 11.75% × 50 days ÷ 365, rounded once, to the penny.

What you can claim

Interest: £16.10
Fixed compensation For a debt of £1,000 to £9,999.99, once per invoice: £70.00
Total to claim: £86.10

On top of the £1,000.00 invoice. Reasonable costs of recovering the debt above the fixed sum can be claimed too.

Claim message

Subject: Late payment interest Hello, The invoice for £1,000.00 was due on 30 June 2026 and was paid on 19 August 2026, 50 days late. Under the Late Payment of Commercial Debts (Interest) Act 1998, statutory interest of 11.75% a year (8% plus the Bank of England Bank Rate of 3.75%) can be charged on late business payments, together with a fixed sum of £70.00 towards the cost of recovering the debt. Interest for 50 days: £16.10 Fixed compensation: £70.00 Total due: £86.10 An invoice for £86.10 is attached. Please get in touch if anything about it is unclear. Kind regards,

Paste it into an email to their accounts team and add your name. gov.uk says to send a new invoice if you add interest to what you are owed.

You can claim£86.10

Days late50

See the working

How statutory late payment interest works

Who can claim it

Any business paid late by another business, or by a public authority. It does not apply to sales to consumers. If your contract sets its own interest for late payment, that applies instead of statutory interest. Source: gov.uk, late commercial payments.

When a payment is late

After the date you agreed. Businesses usually agree up to 60 days, and public authorities must pay within 30. If you never agreed a date, the payment is late 30 days after the customer gets your invoice or you deliver the goods or service, whichever is later.

The rate

8% a year plus the Bank of England Bank Rate in force on 30 June (for interest that starts between 1 July and 31 December) or on 31 December (for interest that starts between 1 January and 30 June). Interest starts the day after the due date. Source: SI 2002/1675, article 4; Bank Rates from the Bank of England.

Statutory interest rates by when interest starts
Interest starts	Bank Rate	Rate a year
Jul to Dec 2024	5.25%	13.25%
Jan to Jun 2025	4.75%	12.75%
Jul to Dec 2025	4.25%	12.25%
Jan to Jun 2026	3.75%	11.75%
Jul to Dec 2026	3.75%	11.75%

Fixed compensation

On top of the interest, once for each late payment: £40 for a debt under £1,000, £70 from £1,000 to £9,999.99, and £100 from £10,000. If recovering the debt costs you more than that, the reasonable extra can be claimed too. Sources: gov.uk, debt recovery costs; section 5A of the Act.

gov.uk's example, and why this says £11.64

gov.uk's worked example is a £1,000 debt when Bank Rate was 0.5%: 8.5% a year is £85, which is about 23p a day, so "after 50 days" it gives £11.50.

That rounds the day to 23p before multiplying. The exact daily amount is £85 ÷ 365 = 23.288p, so 50 days come to £11.64. This calculator works from the annual rate and rounds once, at the end. The gap is small here and grows with the debt and the days.

How to claim

gov.uk says to send a new invoice if you decide to add interest to what you are owed. Send it with a short message like the one above, which has your figures in it. Keep a note of the dates: interest runs until the day they pay.

Questions

Can I charge late payment interest to a private customer?

Not under the Late Payment Act. Statutory interest and the fixed sums are for debts between businesses, including public authorities paying a business. With a private customer you can only charge interest if your contract says so.

Does the rate change while the invoice is unpaid?

No. The rate order ties the rate to the day interest starts to run: the Bank Rate on the 30 June or 31 December before it, plus 8%. That rate applies however long the debt stays unpaid.

Can I claim compensation on every late invoice?

Yes, once for each late payment: £40 for a debt under £1,000, £70 from £1,000 to £9,999.99, and £100 from £10,000. Reasonable recovery costs above that can be claimed as well.