EN 16931: the European e-invoicing standard explained
EN 16931 is the semantic data model behind every EU e-invoice: about 170 business terms, two XML syntaxes (UBL, CII), and business rules (BR). The essentials.
EN 16931 is the European standard on which every compliant EU e-invoice builds. Crucially, it is not a file format but a semantic data model — it defines what data an invoice must carry, not how it is encoded. It stems from EU Directive 2014/55/EU and was developed by CEN/TC 434 (first published 2017).
Building blocks
| Layer | Content |
|---|---|
| Semantics | about 170 business terms (BT) and groups (BG) |
| Syntax | UBL 2.1 and UN/CEFACT CII |
| Rules | business rules (BR-), conditional rules (BR-CO-) |
| CIUS | XRechnung, Peppol BIS, RO_CIUS, Factur-X profiles … |
A business term such as BT-10 (Buyer Reference) maps to concrete XML nodes via the syntax mappings (Part 2 for CII, Part 3 for UBL).
Business rules and CIUS
EN 16931 defines business rules (BR-) that ensure an invoice is valid (e.g. mandatory fields, arithmetic consistency). National and network-specific CIUS (Core Invoice Usage Specifications) such as XRechnung (BR-DE-) or Peppol BIS (PEPPOL-EN16931-*) narrow the standard while staying fully EN-16931-compliant. In 2026 a revised edition, EN 16931-1:2026, was published, partly with the ViDA reporting requirements in mind.
How invowerk helps
invowerk sits precisely at this layer: it validates UBL and CII invoices against the EN 16931 business rules, explains every BR/BR-DE/BR-CO code in plain language (see /codes) and converts between the syntaxes — as an API and an MCP server.