Guide

When is a commercial payment legally late? The 30 and 60 day rules

Updated 2026-08-15

Interest cannot start until the payment is late, and lateness is defined by statute, not by whatever the customer's purchase ledger says its terms are.

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If you did not agree a payment date

gov.uk is explicit: "If you do not agree a payment date, the law says the payment is late 30 days after either: the customer gets the invoice; you deliver the goods or provide the service (if this is later)" (gov.uk). That is the default, and it applies whether the customer is a business or a public body.

If you did agree a payment date

Public authority customer: The agreed date "must usually be within 30 days". Section 4(2D) of the Act makes the relevant day the last day of the 30 day period where that falls earlier than the agreed payment day.
Business customer: The agreed date must usually be within 60 days. You can agree longer, "but it must be fair to both businesses". Section 4(2E) and (2F) put it as a test of whether the agreed day is grossly unfair to the supplier: if it is not grossly unfair, the agreed day stands.

The two 30 and 60 day windows both start on the later of the day you performed your obligation and the day the customer had notice of the amount of the debt (section 4(2H) and (2I)). Sending an invoice after the work is what usually starts the clock.

Then interest runs from the next day

Section 4(2) says statutory interest "starts to run on the day after the relevant day for the debt, at the rate prevailing under section 6 at the end of the relevant day". Two things follow. First, do not count the due date itself when you fill in the days late. Second, the rate is set on that day and does not move afterwards, which is why our calculator asks you for the base rate rather than assuming today's.

A worked sequence

1 April 2026: you complete the work and invoice £10,000. No payment date was agreed.
1 May 2026: 30 days have passed. This is the relevant day.
2 May 2026: statutory interest starts running at 11.75%, the rate fixed by the base rate in force on 31 December 2025.
1 July 2026: 60 days late. Interest stands at £193.15 and the fixed sum at £100, so £293.15 can be invoiced on top of the £10,000.
Interest keeps accruing at £3.22 a day until the debt is paid.

Whether a debt qualifies at all, whether the terms you agreed are grossly unfair, and whether a contractual interest rate has displaced the statutory one are legal questions on your facts. This page explains the statutory framework, it is not advice on your contract.

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Questions, answered directly

How many days after an invoice can I charge late payment interest?

If you agreed no payment date, 30 days after the later of the customer receiving the invoice and you delivering the goods or service. Interest then starts the day after that. If you did agree a date, interest starts the day after it, subject to the caps of 30 days for public authorities and 60 days for businesses.

Can a customer impose 90 day payment terms?

Longer than 60 days can be agreed between businesses, but gov.uk says it "must be fair to both businesses", and the Act tests whether the agreed day is grossly unfair to the supplier. Terms imposed rather than negotiated, on a small supplier, are the situation the test exists for. For public authorities the usual limit is 30 days.

Does interest stop when the customer finally pays?

Yes. Statutory interest runs from the day after the payment was due until the qualifying debt is paid, so the days late figure in the calculator is the number of days from the due date to payment, or to today if it is still outstanding.

Sources

This site's own datasets, every figure quoted from its source and dated:

The median published figure in the Late Payment Prevalence is 50 percent across 2 sources' own pages (range 37 to 63 percent), read 12 October 2026.
The Late Payment Recovery Costs carries 19 published figures read from 3 sources' own pages, from 16 to 10,000 GBP, read 17 October 2026.
The median published figure in the Statutory Late Payment Rate Series is 7.88 percent across 4 sources' own pages (range 3.75 to 8 percent), read 17 October 2026.

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