Late payment interest calculator
An overdue invoice is worth more than the invoice. Work out the statutory interest and the fixed sum you can add to it.
The right reference rate
Fixed by when your debt fell overdue, not by today's base rate.
Interest and the fixed sum
Both entitlements, with the section of the Act each one comes from.
A daily figure
What it grows by every day they hold on to it.
Statutory interest by period
The rate that applies is set by when the debt fell overdue.
- 1 Jul – 31 Dec 2026
- 11.75%
- 1 Jan – 30 Jun 2026
- 11.75%
- 1 Jul – 31 Dec 2025
- 12.25%
- 1 Jan – 30 Jun 2025
- 12.75%
- 1 Jul – 31 Dec 2024
- 13.25%
- 1 Jan – 30 Jun 2024
- 13.25%
Base rate on the reference date plus 8 points. Verified against the Bank of England’s Bank Rate decisions in August 2026.
The two entitlements
Statutory interest
Sections 1 and 6 of the Late Payment of Commercial Debts (Interest) Act 1998. Simple daily interest, from the day after payment was due.
Fixed recovery costs
Section 5A, inserted by the Late Payment of Commercial Debts Regulations 2002. £40, £70 or £100 per invoice, by the size of the debt.
Common questions
How much statutory interest can I charge on a late invoice?
8 percentage points above the Bank of England base rate, under section 6 of the Late Payment of Commercial Debts (Interest) Act 1998. The rate is currently 11.75% a year for debts falling overdue in the current six month period.
Which base rate applies if the invoice has been overdue for months?
The base rate in force on the 30 June or 31 December immediately before the debt fell overdue, not today's rate. That reference rate then applies for as long as the debt is outstanding. Using today's rate is the most common mistake in this calculation, and it is the first thing a debtor's accounts team will pick apart.
Do I need a late payment clause in my contract?
No. Statutory interest is an implied term of every qualifying business to business contract. If your contract does set a different rate for late payment, that rate applies instead.
Now ask them for it
A letter showing these figures and the sections of the Act behind them. First invoice free, and you keep everything you recover.
Related
Other places this tool comes in handy - plus the companies most likely to be on the receiving end.