# EN 16931

European standard defining the semantic data model for e-invoices.

## Definition

European standard defining the semantic data model for e-invoices.

## Why this term matters

EN 16931 is the legal anchor for the EU e-invoicing Directive 2014/55/EU and for ViDA Pillar 1: every public-sector recipient in the EU must accept invoices that conform to it, and every national CIUS (XRechnung, Peppol BIS Billing 3.0, FatturaPA EN16931 mapping, etc.) inherits its semantic model. Misinterpreting BT/BG cardinalities or the EN 16931 codelists is the root cause of most cross-border interop failures.

## Explanation

Defines which business terms (BT) and groups (BG) an EN 16931 compliant invoice can carry.

National implementations can add constraints (CIUS) and extension rules.

## Common mistakes

- Confusing the semantic standard (EN 16931-1) with its syntax bindings (EN 16931-2 for UBL Invoice/CreditNote and CII).
- Sending a free-text VAT category (BT-118) instead of one of the EN 16931 UNCL5305 codes (S, Z, E, AE, K, G, O, L, M).
- Treating BT-1 (invoice number) as numeric — it is a string with sequential semantics, but the spec allows alphanumerics.
- Mismatched totals: BT-109 (Invoice total amount without VAT) must equal sum(BT-131) – sum(BT-92) + sum(BT-99) within rounding tolerance.

## Frequently asked questions

### Is EN 16931 the same as the EU e-invoicing standard?
Yes — Directive 2014/55/EU mandated CEN to publish a European e-invoicing standard, and EN 16931 (multi-part, published 2017, with regular amendments) is the result. Compliance with EN 16931 satisfies the directive’s semantic requirements.

### Which syntaxes are EN 16931 compliant?
EN 16931-2 lists two syntaxes: OASIS UBL 2.1 Invoice and CreditNote, and UN/CEFACT CII D16B Cross-Industry Invoice. Both must be accepted by EU public-sector contracting authorities.

### How do CIUS and Extension differ from EN 16931?
A CIUS (Core Invoice Usage Specification) tightens or restricts EN 16931 (e.g., XRechnung makes BT-10 mandatory). An Extension adds new business terms (e.g., for sectors needing additional structured data). Both must remain backward-compatible with EN 16931 conformance.

## Related resources

- [DIN EN 16931-1 guide](/resources/compliance/din-en-16931-1-standard)

## Related terms

- [CIUS](/resources/glossary/cius): Country or sector specific usage specification that constrains EN 16931.
- [XRechnung](/resources/glossary/xrechnung): German e-invoicing specification for the public sector based on EN 16931.
- [PEPPOL BIS](/resources/glossary/peppol-bis): Business Interoperability Specifications defining document rules (commonly BIS 3.0 for invoices).
- [Business Term (BT)](/resources/glossary/business-term-bt): A standardized data element in EN 16931 (e.g., invoice number, VAT ID).
- [Business Group (BG)](/resources/glossary/business-group-bg): A logical group of business terms in EN 16931 (e.g., seller info, totals).