UK late-payment interest calculator
Estimate simple statutory interest for an eligible business debt. Check the contract and current rate before claiming.
Rates checked:
Who should use this calculator
This free calculator is intended for freelancers, sole traders, contractors and small-business owners who need a quick planning figure before preparing or checking an invoice. It can also help clients and bookkeepers understand the arithmetic behind a quoted amount. Use the result as a review aid alongside the relevant agreement, source records and current official guidance, not as an automatic accounting or legal decision.
Calculator methodology
Debt multiplied by the annual statutory rate, divided by 365, multiplied by days late.
For qualifying UK business-to-business debts, statutory interest is 8 percentage points above the Bank of England base rate. A contract may set a different interest arrangement, so check its payment terms before relying on this estimate.
This is general information, not tax, legal or accounting advice.
Worked example
For an eligible £2,000 business debt that is 30 days late, using an annual statutory rate of 11.75%, the daily interest is approximately £0.64 and the 30-day estimate is about £19.32. Recalculate when the Bank Rate or outstanding principal changes, and retain the rate and dates used.
Important limitations
Statutory interest may not apply where the contract provides another substantial remedy or the debt is not an eligible UK business-to-business payment. The calculator uses simple interest and does not add fixed recovery compensation, legal costs, partial-payment timing or rate changes during the period. Check the agreement and current GOV.UK guidance before making a claim.
Common questions
Does Billoz store my calculator entries?
No. These public calculations run in the browser and are not saved to a Billoz account.
Is the result professional advice?
No. It is an indicative calculation based on the values entered and the displayed method.
Should I keep a record of the calculation?
For an important decision, retain the inputs, result, source and calculation date with the relevant invoice or business record.