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.

• 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.