Hybrid invoices
A simple PDF file is not considered an electronic invoice. The data must be structured, for example in XML format. The EU standard CEN 16931:2017 defines in detail the requirements that electronic invoices must meet. The main formats established on the basis of this standard are the XRechnung and the Factur-X standard (known as a ZUGFeRD invoice in Germany). This latter hybrid format has the advantage of supporting immediate visual display for interactive validation.