# EN 16931 Explained: The European E-Invoicing Standard (2026 Guide) - Date: 2026-01-19 - Reading time: 8 min read EN 16931 is the European standard for e-invoicing. Learn about compliance requirements, CIUS implementations (XRechnung, Factur-X, UBL), and how it affects... ## Article overview This article explains EN 16931 Explained: The European E-Invoicing Standard (2026 Guide) as a practical reference for European e-invoicing. It defines the topic in plain language, places it in the compliance context, and connects the explanation to invoice formats such as XRechnung, ZUGFeRD/Factur-X, UBL, and CII. Use the article as a starting point before changing a finance or ERP workflow: identify the applicable country rule or standard, decide which structured format is expected, validate the generated XML, and keep a documented exception process for invoices that require manual review. ## 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, EU public procurement recipients covered by the e-invoicing directive must be able to receive and process EN 16931 e-invoices. B2B mandates are rolling out country by country, so understanding EN 16931 is essential for businesses that invoice across Europe. ### 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 receiver covered by a specific mandate must support the syntaxes and CIUS required for that mandate. Do not assume every buyer accepts every EN 16931 CIUS; check the buyer’s country, network, platform, and onboarding rules. ### 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 - Receivers still need to support the specific syntax, CIUS identifier, network route, and platform process used for delivery #### 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 when required by the recipient or local CIUS (e.g., Leitweg-ID in German public-sector flows) - **BT-27 to BT-35**: Seller information - **BT-44 to BT-52**: Buyer information - **BT-126 to BT-153**: Line item details - **BT-116 to BT-120**: VAT breakdown 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 designed to align with EN 16931 requirements: - 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 [Explore EN 16931-ready formats →](/en) ## How to use this guide Use the article as a starting point before changing a finance or ERP workflow: identify the applicable country rule or standard, decide which structured format is expected, validate the generated XML, and keep a documented exception process for invoices that require manual review.