Knowledge Base

Guides

Background articles on the standards, formats, and country-specific rules behind European e-invoicing.

• What is EN 16931? A guide to the European e-invoice standard

  EN 16931, the European e-invoice standard, explained: semantic data model, UBL vs CII, CIUS customisations, validation rules, and what falls inside and outside the standard.

• E-invoicing in Germany: requirements, formats, and timeline

  Germany's transition to mandatory electronic invoicing under §14 UStG: timeline, accepted formats (XRechnung and ZUGFeRD), B2G and B2B channels, archival under GoBD, and practical advice.

• Factur-X and ZUGFeRD: the hybrid PDF/XML invoice

  Factur-X (a.k.a. ZUGFeRD) explained: the hybrid PDF/A-3 with embedded CII XML, its five profiles, when to use it, and where the format does not help.

• UBL vs CII: the two XML syntaxes of EN 16931

  EN 16931 endorses two XML syntaxes — UBL 2.1 and UN/CEFACT CII. Both express the same semantic model. A practical comparison of where each comes from, what they look like, and where each dominates today.

• What our 'Accepted' verdict means — and what it doesn't

  A green CIUS-validation report tells you a document is structurally well-formed against an agreed shape. It does not tell you the document is sufficient under any particular country's VAT law. The two questions are separate, and the gap is where most confusion lives.

• XRechnung vs ZUGFeRD: which to use, and when

  The two are not competing formats — they are different approaches to the same problem. A practical comparison of pure-XML XRechnung against the hybrid PDF/XML ZUGFeRD, with a recommendation for each scenario.

• XRechnung: the German CIUS for electronic invoicing

  XRechnung explained: Germany's national CIUS on top of EN 16931, the BR-DE-* rule additions, the Leitweg-ID, the XRechnung Extension, and what the specification covers and excludes.

Validation Rules Reference (1984)

Complete reference of all EN 16931, XRechnung, PEPPOL BIS, and Factur-X validation rules with explanations and fix suggestions.