EN 16931
EN 16931 is the European standard that defines a common semantic data model for the core elements of an electronic invoice.
EN 16931 sets out what fields an invoice must carry and what they mean: seller, buyer, line items, VAT breakdown, totals. It is the shared foundation under XRechnung, ZUGFeRD and Factur-X.
Because national formats are all defined against EN 16931, an invoice created in one country can be understood in another. The standard is expressed through two allowed syntaxes, UBL and CII.
Cortena maps every incoming e-invoice through the EN 16931 model before coding it.