EN 16931 Explained: The European E-Invoicing Standard (2026 Guide)
What is EN 16931? The Foundation of European E-Invoicing
EN 16931 is the European standard for electronic invoicing, established by the European Committee for Standardization (CEN). Published in June 2017, it defines the core data model and semantic rules that all compliant e-invoices must follow across the European Union.
Since April 18, 2019, all public contracting authorities in the EU are obliged to accept electronic invoices in the EN 16931 format. Now, with B2B mandates rolling out across Europe in 2026, understanding EN 16931 is essential for every business.
Why EN 16931 Matters
EN 16931 solves a fundamental problem: before this standard, each country and industry had different e-invoice formats that couldn't communicate with each other. EN 16931 creates a common language that enables:
- Cross-border interoperability - Send invoices to any EU country
- Automated processing - Machines can read and process invoices without human intervention
- Reduced errors - Standardized data means fewer mistakes
- Lower costs - No need for custom integrations per country or partner
The Three Compliance Levels
EN 16931 defines compliance at three levels, and each party must comply with all:
1. Invoice Document Compliance
The electronic invoice document itself must comply with all rules defined for the CORE invoice model or an approved CIUS specification. This includes:
- All required data elements present
- Correct data formats (dates as YYYY-MM-DD, currencies in ISO 4217)
- Valid calculations (totals, taxes)
- Proper XML structure
2. Sender Compliance
A compliant sender must be able to create electronic invoices that conform to EN 16931 CORE or a CIUS. Your invoicing system must generate properly structured invoices.
3. Receiver Compliance
A compliant receiver must accept and process all invoices that conform to EN 16931 CORE or any CIUS. You cannot reject an invoice solely because it uses a different CIUS than you prefer.
Approved Syntaxes
EN 16931 allows two technical syntaxes for encoding the invoice data:
| Syntax | Description | Common Usage |
|---|---|---|
| UBL 2.1 | Universal Business Language | Peppol, Belgium, Netherlands |
| UN/CEFACT CII | Cross Industry Invoice | Germany (XRechnung), France (Factur-X) |
What is a CIUS?
CIUS stands for Core Invoice Usage Specification. Think of it as a country-specific or sector-specific adaptation of EN 16931. While the standard defines general rules, a CIUS narrows them down for local requirements.
Key CIUS rules:
- A CIUS must be a subset of the CORE - it cannot add new fields
- A CIUS cannot break any CORE rules
- Anyone who can receive CORE can receive any compliant CIUS
Major CIUS Implementations
| CIUS | Country | Syntax |
|---|---|---|
| XRechnung | Germany | UBL 2.1 or CII |
| ZUGFeRD 2.x | Germany, Austria | CII (embedded in PDF) |
| Factur-X | France | CII (embedded in PDF) |
| Peppol BIS | EU-wide, Belgium, NL | UBL 2.1 |
| NLCIUS | Netherlands | UBL 2.1 |
Required Fields in EN 16931
EN 16931 uses "Business Terms" (BT) to identify invoice fields. Key required fields include:
- BT-1: Invoice number
- BT-2: Invoice issue date
- BT-3: Invoice type code
- BT-5: Invoice currency code
- BT-10: Buyer reference (e.g., Leitweg-ID in Germany)
- BT-27 to BT-35: Seller information
- BT-44 to BT-52: Buyer information
- BT-109 to BT-115: Line item details
- BT-116 to BT-118: Tax information
EN 16931 and 2026 Mandates
Several European countries now require EN 16931 compliance for B2B transactions:
| Country | Mandate Date | Format |
|---|---|---|
| Belgium | January 2026 | Peppol BIS (UBL) |
| France | September 2026/2027 | Factur-X, UBL, CII |
| Germany | January 2027/2028 | XRechnung, ZUGFeRD |
How to Validate EN 16931 Compliance
Before sending an e-invoice, you should validate it against EN 16931 rules. Validation checks include:
- Schema validation - Correct XML structure
- Schematron rules - Business rule compliance
- CIUS-specific rules - Country-specific requirements
How Invoice-Converter Ensures EN 16931 Compliance
Invoice-Converter.com generates e-invoices that are fully compliant with EN 16931:
- Converts PDF invoices to XRechnung, ZUGFeRD, UBL, and Factur-X
- Automatically validates against EN 16931 rules
- Supports all major CIUS implementations
- Ensures correct BT field mapping
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