EN 16931 is the European standard for electronic invoicing, developed by the European Committee for Standardization (CEN) at the request of the European Commission. Most European e-invoice formats are built on it.
What the standard contains
- Part 1 (EN 16931-1:2017) — the semantic data model: which information an invoice contains (business terms) and the business rules.
- Part 2 (CEN/TS 16931-2:2017) — the two syntaxes that may carry the model: UBL 2.1 and UN/CEFACT CII.
- Part 3 — syntax bindings that map each business term to a path in UBL or CII.
CIUS and extensions
A CIUS (Core Invoice Usage Specification) narrows the standard, for example by making optional fields mandatory. An extension adds elements, code values or meanings. Examples of CIUSs: XRechnung, Peppol BIS Billing 3.0, NLCIUS, CIUS-PT and RO_CIUS.
Why it matters
Directive 2014/55/EU requires public contracting authorities in the EU to accept EN 16931 e-invoices (at least above EU procurement thresholds). Several national B2B mandates also reference the standard, for example Germany's definition of an e-invoice from 2025.
Limits
- The standard defines content, not delivery: you still need a channel (Peppol, a national platform, e-mail where allowed).
- An invoice can be valid EN 16931 and still fail a national CIUS.
More detail: EN 16931 format page.