What this calculates
Enter your invoice date and the payment terms you agreed, and the calculator gives you the exact payment due date — plus the day after, when your rights under the Late Payment of Commercial Debts (Interest) Act 1998 switch on:
- Statutory interest at 8 percentage points above the Bank of England base rate, accruing daily from the day after payment was due.
- Fixed compensation per late invoice: £40 for debts under £1,000, £70 for £1,000–£9,999.99, £100 for £10,000 or more.
The 30-day default
If your contract says nothing about payment terms, the Act implies a 30-day term — payment is due 30 days after you performed the work or sent the invoice, whichever is later. That is why the calculator defaults to 30 days.
Agreed longer terms
You and your client can agree longer terms, but there is a limit. Under the Act, payment terms of more than 60 days must not be “grossly unfair” to you — very long terms can be challenged. (A Commercial Payments Bill before Parliament would cap business-to-business terms at 60 days outright, but as of October 2026 it is not yet law.) If you entered more than 60 days above, the calculator flags it — worth a conversation before you sign.
Once it is overdue
Knowing the due date is step one. Step two is knowing what the late payment is costing them: our late-payment interest calculator works out the exact interest and compensation figure, with a line you can paste into your chasing email. For the full picture of your rights, read our plain-English guide to UK late-payment law.
This page explains publicly available information from gov.uk, the Bank of England and the legislation itself, verified on 18 October 2026. It is not legal advice. For a disputed or high-value debt, speak to a solicitor.