UK Late Payment Interest Calculator (statutory 8% plus base rate, £40/£70/£100 compensation)

How much can I charge on a late business invoice?

Enter the unpaid amount and the due date. You get the statutory interest (8% over the Bank of England base rate), the fixed compensation, the daily rate, where the total will be in 30, 60 and 90 days, and a demand letter with your figures filled in.

For invoices between two businesses. Base rates are built in from 2023; check them on GOV.UK. Not legal advice.

Unpaid invoice amount (£)

When was it due?

Due date, or invoice/delivery date (YYYY-MM-DD)

Work out the figure as at (YYYY-MM-DD)

Who owes it?

Base rate % (leave blank to use the built-in one)

Reasonable recovery costs so far (£, optional)

Your business name (for the letter)

Customer name (for the letter)

Invoice reference (for the letter)

Fill in the figures, then click Work out what I can claim.

Result

If it stays unpaid

Date	Interest	Total due

What to do

Step	What it means

Demand letter

What it does, and what it leaves to you

Covers: one overdue invoice between two businesses (or a public body): statutory simple interest at 8% over base rate, the fixed compensation tier, optional recovery costs and a demand letter.
Gives: the amount claimable today, the daily interest, a 30/60/90 day projection and a letter to adapt.
Not decided: whether your contract displaces the statutory rate, disputed invoices, part payments, debts owed by individuals, court procedure and fees, and anything that changed after this was written.

Common questions

How much interest can I charge on a late business invoice in the UK?

Under the Late Payment of Commercial Debts (Interest) Act 1998 you can claim statutory interest at 8% a year over the Bank of England base rate. The base rate used is the one on 31 December for debts that fell due January to June, or on 30 June for debts due July to December. Interest is simple and runs from the day after the due date.

What fixed compensation can I claim?

A fixed sum per late invoice: £40 for debts under £1,000, £70 for £1,000 to £9,999.99, and £100 for £10,000 or more. You can also claim reasonable debt recovery costs if the fixed sum does not cover them.

When does a business invoice become late if no date was agreed?

Under the Act the default is 30 days after the later of the invoice being received and the goods or services being delivered. If you agreed a payment date or terms, that date applies.

Does this apply to consumers?

No. The Act covers contracts where both sides are acting in the course of a business, or a public body is the buyer. It does not cover debts owed by private individuals.

Can I write a different late fee into my terms?

Contract terms can set their own interest only if they provide a substantial remedy for late payment; otherwise the statutory rate applies. Check this with a solicitor if it matters.

Is my data uploaded anywhere?

No. Everything is calculated in your browser and nothing is sent.