Late Payment Interest Calculator
This late payment interest calculator works out the statutory interest and fixed compensation you can claim on late commercial invoices. Add every overdue invoice, not just one.
| Invoice | Outstanding | Days late | Interest | Compensation | Claim |
|---|---|---|---|---|---|
| INV-1042 | £6,400.00 | 38 | £78.29 | £70.00 | £6,548.29 |
This works out what the legislation entitles you to so you can put a figure on a demand. It isn't legal advice — whether interest is claimable depends on your contract and the nature of the debt. How to charge late payment interest explains the rules in full.
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When another business pays you late, you are entitled to interest and a fixed sum on top — automatically, whether or not it is written into your contract. Most trades never claim it, because working it out across several invoices is a faff.
If you just resend the invoice and hope, you carry the cost of the delay yourself. The interest and the fixed sum are there to compensate you for exactly that, and you do not need permission to claim them.
This calculator does the whole claim. Add every overdue invoice, knock off anything paid on account, and it works out the statutory interest on each one, applies the right fixed compensation band, and totals what you are owed today.
What you can actually claim
Enter each overdue invoice and its due date, and the calculator shows the full claim.
How the claim is built
A 6,400 invoice 38 days late: 78.29 interest plus 70 compensation.
6,400.00
78.29
70.00
6,548.29
2.06
The part most calculators miss
The fixed compensation is claimable once per late invoice, not once per claim. Chasing four invoices means four fixed sums on top of the interest, and almost nobody adds them up.
On smaller invoices that fixed sum is the larger half of what you are owed. A 600 invoice 20 days late earns about 3.86 in interest and a 40 fixed sum on top.
Read the full rules
It is a right, not a negotiation
Statutory interest runs at 8% above the Bank of England base rate — 11.75% as at August 2026. It is simple interest: the outstanding balance times the rate, divided by 365, times the number of days late. It runs from the day after payment was due until the day you are paid.
On top of the interest, each late invoice carries a fixed compensation sum: £40 up to £999.99, £70 from £1,000 to £9,999.99, and £100 at £10,000 or more. It is claimable once per late payment, so five late invoices carry five fixed sums. On a small invoice that fixed sum is usually the bigger half of the claim — a £600 invoice 20 days late earns about £3.86 of interest and a £40 fixed sum.
How long you can chase it
Who is this calculator for?
Keep the invoice, the payment and the dates together
Claiming it depends on being able to show what was owed and when it was paid. Keeping every invoice, payment and part payment dated in one place means the arithmetic is already there when you need to put a figure on a demand.
Chase it properly before you claim
Use these alongside your late payment claim.
Statement of Account Generator
Show every invoice, payment and how old the balance is.
Build a statement →Free tools for the job
Put these numbers to work — free FieldHive tools, no sign-up.
Statement of Account Generator
Show a customer every open invoice and payment with a balance now due and an ageing summary.
Statement of Account Generator →Free Invoice Generator
A correct UK invoice for sole traders and the self-employed — right VAT handling, sole trader vs limited company, optional late-payment interest.
Invoice Generator →Trade Business Break-Even Calculator
Find the revenue you need to break even.
Trade Business Break-Even Calculator →Late payment interest questions
Quick answers to the questions people ask most.
Claim what you are owed on late invoices
Work out the interest and compensation on every overdue invoice, then keep the whole job connected with FieldHive.
