Free tool
Work out the interest on a late invoice.
For a late payment from one UK business to another. Enter the amount and the dates. You see the interest the law allows, and the fixed sum you can add for the cost of chasing.
The amount still owed, including VAT if you charged it.
Still unpaid? Leave today's date.
Filled in: 3.75%, the rate on 30 June 2026 (checked 8 October 2026). You can change it. Bank of England: Bank Rate
- Days late
- Interest rate
- Interest a day
- Interest so far
- Fixed sum for recovery costs
- Interest and fixed sum
- Invoice, interest and fixed sum
A guide to the law, not legal advice. It works for a debt between two businesses with no other interest rate in the contract.
How it works
The sum, step by step.
The same steps GOV.UK uses. Simple interest, worked out by the day.
- Find when it became late. That is the day after the agreed due date. With no agreed date, a payment is usually late 30 days after the customer got the invoice or the work was done, whichever is later. GOV.UK: when a payment becomes late
- Find the rate. Statutory interest is 8% a year plus the Bank of England base rate. Source: GOV.UK
- Use the right base rate. It is the rate on a fixed date, not today's. If interest starts between 1 January and 30 June, use the rate on 31 December before. If it starts between 1 July and 31 December, use the rate on 30 June. The rule in law
- Work out a day's interest. Take a year's interest on the amount owed, divide it by 365 and round it to the penny.
- Multiply by the days late. Count from the day after the due date to the day you are paid.
- Add the fixed sum. It depends on the amount owed. You can claim it once for each payment. GOV.UK: recovery costs
GOV.UK's own example: £1,000 owed, with a base rate of 0.5%. A year's interest at 8.5% is £85. That is about 23p a day, so after 50 days the interest is £11.50. GOV.UK: charging interest
Before you claim
When you can, and when you cannot.
| Amount owed | Fixed sum you can claim |
|---|---|
| Up to £999.99 | £40 |
| £1,000 to £9,999.99 | £70 |
| £10,000 or more | £100 |
- It is for payments between businesses, not for sales to the public.
- If your contract sets its own rate of interest, that rate applies instead.
- If you add interest, send the customer a new invoice that shows it.
- It is your choice. Many firms mention it in their terms and on a final notice, then decide case by case.
Sources checked on 8 October 2026. Copy a final notice that names the interest
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