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Starter plan

Late Payment Interest Calculator UK

Calculate statutory interest under the Late Payment of Commercial Debts Act 1998 and generate a professional demand letter in under 60 seconds.

Calculate interest & generate letter

Included in Starter (£7/mo) and Pro (£12/mo) plans.

Fixed compensation by invoice value

In addition to interest, you are entitled to a fixed compensation payment.

£40 fixed compensation

Invoice < £1,000

£70 fixed compensation

£1,000 – £9,999.99

£100 fixed compensation

£10,000 or more

Sample output

Illustrative output — £4,500 invoice, 45 days overdue, B2B client.

Late Payment Calculation

Invoice amount£4,500.00
Days overdue45 days
Statutory rate (BoE 4.75% + 8%)12.75% p.a.
Interest accrued£70.51
Fixed compensation (£1K–£10K tier)£70.00
Total amount now due£4,640.51
Demand letter excerpt: “Pursuant to the Late Payment of Commercial Debts (Interest) Act 1998, we hereby claim statutory interest of £70.51 and fixed compensation of £70.00 on Invoice #1042, which became due on [date]. The total sum of £4,640.51 must be paid within 7 days…”
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Common questions

What statutory interest rate can I charge on late invoices?

Under the Late Payment of Commercial Debts (Interest) Act 1998, you can charge 8% per annum above the Bank of England base rate. At the current BoE base rate of 4.75%, the total rate is 12.75% per annum.

Does this apply to consumer clients too?

No — statutory late payment interest under the 1998 Act applies to business-to-business contracts only. For consumer clients you would need to rely on any contractual late payment clause in your terms.

Do I have to include late payment terms in my contract?

No. Statutory interest applies automatically to all B2B contracts for goods and services, even if your contract is silent on late payment. You do not need to include any specific wording.

How does FFCC generate the demand letter?

Claude AI creates a professional demand letter citing the Late Payment of Commercial Debts (Interest) Act 1998, the exact interest calculation, the applicable fixed compensation, and a payment deadline. You can download it as PDF (Pro plan) or copy the text.

Stop chasing invoices. Start charging interest.

Demand letter in under 60 seconds. Starter plan — £7/month.

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