Invoices are issued according to the rules of the country of destination. Invoice issuers from outside Germany who are “entrepreneurs” as defined in section 14 of the German Civil Code (Bürgerliches Gesetzbuch, BGB) and who are involved in public procurement transactions with the federal administration, as referred to in section 1 of the E-Invoicing Ordinance (E-Rechnungsverordnung, ERechV), are obliged to issue electronic invoices in compliance with the E-Invoicing Ordinance.