An unpaid invoice is not just late — in many jurisdictions it is quietly earning you interest, and in some, a fixed compensation fee on top. Pick your jurisdiction: the statutory rate prefills, and the calculator shows the total owed and how much it grows every day.
60 days overdue
UK default: 11.75% per year
Total now owed to you · UK
£5,166.58
£5,000 principal · 60 days overdue at 11.75%
Simple interest: amount × (11.75% ÷ 365) × 60 days + fixed compensation fee. Information, not legal advice — contract terms can override statutory defaults.
Each guide covers the statutory rate and basis, fixed fees, a worked example, and a demand-letter checklist — with sources and verification dates.
Europe and the anglosphere split sharply on this. In the UK, Ireland, and across the EU, late payment interest is a statutory right: a fixed margin (8 percentage points) above a central bank reference rate, plus fixed compensation per invoice, with no contract clause required. In the US, Australia, and Canada, your contract does the work — statutory “legal rates” exist as fallbacks, but they are generally weaker and often only bite once you litigate.
The practical lesson is the same everywhere: put a late-payment clause in your terms before the work starts, invoice with a clear due date, and when a payment slips, send the number — principal, interest to date, and the daily accrual — rather than a plea. Every page here computes that number for you.