In general, invoices for the federal administration must be issued using the currently valid XRechnung standard. Other standards may be used (such as ZUGFeRD version 2.1.1 or later in the XRECHNUNG profile, as a simple structured XML file) as long as they meet the requirements of the European standard (EN 16931), the terms of use for the invoice submission portals, and the requirements of the federal E-Invoicing Ordinance.