The UK's current late payment laws are, in part, due to an EU Directive designed to standardise the right to claim late payment interest on overdue commercial bills throughout its member states.
Most, though not all, EU member states have implemented late payment legislation based on this Directive. Click here for a list of countries that have implemented the Directive.
Broadly speaking, the Directive provides for a 30-day period in which bills must be paid, after which penalty interest of 7 percentage points above the ECB rate can be charged (although countries not in the euro zone can set their own rates above their own national base rate, as in the UK).
If you do want to claim late payment interest please use the Directive as guideline but please remember that the laws are different in each EU state.