UBL vs CII — the two e-invoice syntaxes
UBL and CII are the two standardized XML syntaxes for EN 16931 invoices. UBL (OASIS) is used by Peppol, XRechnung and most European networks; CII (UN/CEFACT) underpins ZUGFeRD/Factur-X hybrids. Semantically equal, syntactically different — converters map between them losslessly for core content.
The short comparison
| UBL 2.1 | UN/CEFACT CII | |
|---|---|---|
| Standards body | OASIS | UN/CEFACT |
| Used by | Peppol BIS, XRechnung (variant), NLCIUS, OIOUBL, e-SLOG | ZUGFeRD / Factur-X, XRechnung (variant) |
| Style | many small documents (Invoice, CreditNote, Order…) | one large cross-industry schema |
| Hybrid PDF | rare | standard (embedded in PDF/A-3) |
Both carry the same EN 16931 semantics — the choice is ecosystem-driven, not technical. Peppol standardised on UBL, so everything on the network, including the documents this site describes, is UBL. See EN 16931 for the semantic layer both share.
Updated: August 29, 2026