UK Late Payment Interest Calculator (2026)

Calculate the statutory interest and fixed compensation you can claim on a late-paid UK B2B invoice under the Late Payment of Commercial Debts (Interest) Act 1998. Current statutory rate: 11.75% APR (Bank of England base rate 3.75% plus 8%).

Last updated: 8 May 2026.

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UK statutory late payment interest is 11.75% APR (BoE base 3.75% + 8%) under the Late Payment of Commercial Debts (Interest) Act 1998, plus £40, £70 or £100 fixed compensation by debt size. The right is automatic on UK B2B contracts.

Summary

This calculator computes statutory late payment interest and fixed compensation for any unpaid UK B2B invoice. Inputs: invoice amount, due date, payment date or today. Outputs: daily interest rate, total interest accrued, fixed compensation charge by debt size, and total now due. Updated for 2026 Bank of England base rate of 3.75%.

This Page Covers

UK statutory late payment interest calculation: statutory rate, fixed compensation, day count, claim method

Not Covered Here

General invoice finance education (see /guides/), individual provider reviews (see /providers/), full late payment legal guide (see /unpaid-invoices/late-payment-interest-rate/)

Calculator

How the calculation works

Daily interest = Invoice principal x annual rate divided by 365. Multiply by days overdue (paid date minus due date). Add the fixed compensation charge by debt size: £40 under £1,000, £70 between £1,000 and £10,000, £100 at £10,000 and above.

Worked example: £5,000 invoice, 60 days overdue, statutory 11.75% rate. Daily interest = (5000 x 0.1175) / 365 = £1.61. Sixty days = £96.58. Plus £70 fixed compensation = £166.58 total interest and compensation owed on top of the £5,000 principal. Total now due: £5,166.58.

When statutory interest applies

The right applies automatically to any UK B2B contract where no other interest rate is contractually agreed. It does not apply to consumer transactions or contracts where you've agreed an alternative substantial remedy. You can claim statutory interest even if the customer eventually pays the principal.

If the customer still won't pay

After 30 days overdue, send a letter before action. After 14 days more without payment, you can issue a money claim online, file a statutory demand if the debt is over £750, or sell the invoice for immediate cash.

OM

Oliver Mackman

Director, Market Invoice

Oliver leads Market Invoice's editorial and comparison research. With a background in UK commercial finance, he oversees provider analysis, rate verification, and industry reporting across all verticals.

Last reviewed: 8 May 2026

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UK Late Payment Interest Calculator FAQ

What is the UK statutory late payment interest rate?

11.75% APR. Bank of England base rate (currently 3.75% as of March 2026) plus 8 percentage points. Set by the Late Payment of Commercial Debts (Interest) Act 1998 and updated whenever the Bank of England base rate changes.

How much fixed compensation can I claim?

Under £1,000: £40. £1,000 to £9,999.99: £70. £10,000 or more: £100. Per overdue invoice, on top of the interest charge.

When does interest start running on a late paid UK invoice?

From the day after the agreed payment date. If your contract specifies 30-day terms, interest accrues from day 31. If no terms are agreed, the default under the Act is 30 days from invoice or delivery, whichever is later.

Can my customer opt out of statutory late payment interest?

Only by contractually agreeing a 'substantial remedy' equivalent to the statutory rate. A clause that simply removes the right to interest is unenforceable. The statutory rate is the floor for B2B late payment compensation in the UK.

Do I need a court order to claim late payment interest?

No. The right is automatic for any UK B2B contract where no other interest rate is contractually agreed. You can add the calculated interest and compensation directly to your final demand or next invoice.

How do I claim the interest in practice?

Issue a final demand listing the original invoice value, days overdue, calculated daily interest (use the calculator above), the fixed compensation charge, and the total now due. Send by email and recorded delivery. If unpaid, you can pursue the combined amount in small claims court without a separate interest claim.