Free tool

UK Late Payment Interest Calculator

Work out the statutory interest and fixed compensation you can claim on an overdue commercial invoice — instantly, in your browser, with no signup. Based on the Late Payment of Commercial Debts (Interest) Act 1998.

Use the BoE base rate in force on the day the payment became late — check bankofengland.co.uk.

Enter your invoice amount and how many days it is overdue to calculate the statutory interest and compensation you can claim.

Optional. We'll only use it to send your results and occasional invoicing tips.

How late payment interest is calculated

When a business customer pays a commercial invoice late, UK law lets you charge statutory interest on the unpaid amount. For business-to-business debts that rate is 8% per year plus the Bank of England base rate in force on the day the payment became late.

The calculation is:

  • Annual rate = 8% + base rate
  • Daily interest = invoice amount × (annual rate ÷ 100) ÷ 365
  • Interest owed = daily interest × days overdue

On top of the interest you can also claim a one-off fixed compensation per invoice to cover your recovery costs:

  • Invoice under £1,000 → £40
  • £1,000 to £9,999.99 → £70
  • £10,000 or more → £100

This tool is for commercial (B2B) debts. Debts owed by consumers are governed by different rules, so do not use these figures for them. The result is an estimate to help you chase payment — it is not legal advice, and your contract may set a different agreed remedy.

Want the full breakdown, including how to add interest to an invoice and word a reminder? Read the full guide to charging late payment interest and fees in the UK →

Late payment FAQ

How much interest can I charge on a late payment?

For commercial (business-to-business) debts in the UK, statutory interest is 8% per year plus the Bank of England base rate in force on the day the payment became late. You can charge this on overdue invoices unless your contract sets a different, substantial remedy.

How is statutory late payment interest calculated?

Multiply the unpaid invoice amount by the annual rate (8% + base rate), divide by 365 to get the daily interest, then multiply by the number of days the payment is overdue. For example, on a £1,000 invoice at a 12.75% rate, daily interest is about £0.35, so 30 days overdue is roughly £10.48.

What is the fixed compensation for late payment?

On top of interest you can claim a fixed sum per invoice: £40 for debts under £1,000, £70 for debts of £1,000 to £9,999.99, and £100 for debts of £10,000 or more.

Does this apply to consumer debts?

No. The statutory interest and compensation calculated here apply to commercial (B2B) debts under the Late Payment of Commercial Debts (Interest) Act 1998. Debts owed by consumers are governed by different rules, so this tool should not be used for them.

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