Late payment interest calculator
What you are legally entitled to claim when another business pays late — interest, plus a fixed sum. Free, nothing to sign up for.
30 days where your contract says nothing.
Pre-filled with the rate as at 12/10/2026, which is not kept up to date — check the current one before you quote it.
- Days late
- 60
- Interest at 12%
- £94.68
- Fixed sum
- £70.00
- Claimable on top
- £164.68
Payment was due 16/08/2026. You can claim £164.68 on top of the £4,800.00 itself, and it grows by £1.58 a day. Saying that figure in the email is usually what gets the invoice paid.
Base rate plus eight, simple, from the day after it was due
Statutory interest is not compound and it does not start on the due date itself — an invoice paid on the day it fell due is not late and is worth nothing extra. From the next day it accrues daily on the unpaid amount.
The base rate moves, so the figure here is only as good as the rate you put in. The field is pre-filled and dated, and it is not kept up to date automatically: check the current one before you quote it in writing.
The fixed sum is a band, and the boundaries are exact
£40 below £1,000, £70 from £1,000 to £9,999.99, and £100 at £10,000 and above. A debt of exactly £1,000 is £70, not £40 — which is the sort of detail the other side will correct you on if you get it wrong, and it undermines the rest of the letter.
Naming the figure is usually the point
Most trades never actually claim it. What works is the email: the invoice is X days late, £Y is already claimable under the 1998 Act, and it grows by £Z a day. It is specific, it is checkable, and it moves an invoice up somebody’s payment run without a phone call.
Keep your terms clear about payment dates, because that is what the whole entitlement hangs on.
A note on what this is
A guide, not advice, and it cannot know everything about your arrangement. Check anything that matters with your accountant.
Built by TaskMyJob, which does this on every invoice it raises. More free reading: chasing what you are owedraising an invoiceall the guides.