EN 16931

Also called European Norm 16931, the European e-invoicing standard

EN 16931 is the European standard that defines the semantic data model for an electronic invoice: a fixed set of named business terms, and the rules that govern how they relate. It is deliberately syntax neutral, so the same invoice can be expressed as CII or UBL and still be the same EN 16931 invoice.

Published by: CEN, the European Committee for Standardization
Business rules: 223, published as Schematron
Syntaxes: CII and UBL
Field naming: BT- for business terms, BG- for business groups

A vocabulary, not a file format

The standard says an invoice has a buyer VAT identifier, that it is called BT-48, and what it means. It does not say where that sits in a file. Two syntaxes carry it: CII and UBL. Both are legitimate and both are EN 16931.

That separation is why Factur-X, ZUGFeRD, XRechnung and PEPPOL BIS can all be "EN 16931 based" while looking nothing alike as files. They share the meaning and differ in the packaging.

The rules are machine readable, which is unusually helpful

EN 16931 publishes its business rules as Schematron, so "does this invoice comply" is a question with a definite answer rather than an opinion. 223 rules cover required fields, arithmetic, decimals, code lists and VAT category conditions.

The catch is that the rule text is written in the vocabulary of the specification. BR-CO-15 tells you that BT-112 must equal BT-109 plus BT-110, which is precise and close to useless to the person who has to fix the invoice. We wrote a plain language explanation for every one of the 223.

Why it matters

Every European mandate is written around it, so an invoice that satisfies EN 16931 is most of the way to satisfying any of them.
Most of the way is not all of the way. National CIUS rules sit on top, and passing the European standard says nothing about those.

Check it on your own file

All 223 rules explained
Grouped by what actually went wrong, with the cause and the fix for each.
Validate against the official Schematron
The CEN artefacts, compiled and run in your browser, so the invoice is never uploaded.

Common questions

Is EN 16931 a file format?: No. It is a semantic model: which fields exist and what they mean. CII and UBL are the two syntaxes that express it, and both are equally valid.
How many rules does EN 16931 define?: 223 business rules, published as machine readable Schematron. They cover required fields, arithmetic consistency, decimal places, code lists and the conditions attached to each VAT category.