EN 16931
The European standard defining the semantic core of an e-invoice — the common data model behind XRechnung, ZUGFeRD/Factur-X and Peppol billing.
What EN 16931 is
EN 16931 is the European norm that defines what an electronic invoice must contain — not how it looks, but which pieces of information it carries and what they mean. It was developed by the European standardization committee CEN/TC 434 following Directive 2014/55/EU on electronic invoicing in public procurement, and has since become the anchor for e-invoicing far beyond the public sector.
The semantic model
The heart of the standard is a semantic data model: a catalogue of business terms (BT) and business groups (BG) — seller, buyer, line items, VAT breakdown, payment terms and so on — each with a defined meaning, cardinality and set of business rules. Two XML syntaxes are permitted to express this model:
An invoice conforms to EN 16931 when it carries the required terms in one of these syntaxes and passes the associated validation rules.
CIUS: national profiles
Countries and networks adapt the core through a CIUS (Core Invoice Usage Specification), which may tighten the standard but never contradict it. XRechnung is Germany's CIUS; Peppol BIS Billing 3.0 is the CIUS used across the Peppol network; ZUGFeRD 2.x / Factur-X embeds EN 16931-conformant XML in a PDF. This layering is why an invoicing system that models EN 16931 correctly can serve several output formats from a single data set.
Why it matters in Germany
Germany's domestic B2B e-invoicing rules define an electronic invoice as one that conforms to EN 16931 or an interoperable format agreed between the parties. Since January 2025 businesses must be able to receive such invoices; obligations to issue them follow in stages from 2027. Whether a document legally counts as an e-invoice therefore hangs directly on this standard.
In agency practice
For an agency the standard is mostly invisible plumbing — until a client's accounts-payable system rejects an invoice because a mandatory business term is missing or a VAT category code is wrong. Understanding that the required fields, not the layout, decide compliance helps a lot when negotiating invoicing requirements with enterprise brands and public-sector clients.
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