Late payment interest calculator
Work out the late-payment interest accruing on an overdue invoice from the days and the interest rate.
Late-payment interest compensates for a delayed payment: interest = amount × rate × days ÷ 365. Enter the unpaid amount, the number of days overdue and the annual interest rate.
Which rate?
Agreed interest: the rate set in the contract or on the invoice. Statutory interest (when nothing is agreed, LOA § 113): the interest rate applied to the European Central Bank main refinancing operations (as of 1 January / 1 July of the half-year) plus 8 percentage points. Check the current base rate and use your contract rate if it differs.
Sources
Based on official sources · last reviewed 2026-07-17.