UBL vs. CII: The Two XRechnung Syntaxes Compared

Updated: 2026-06-25

Anyone looking into the XRechnung soon runs into two abbreviations: UBL and CII. Both are valid — but what is the difference?

Same model, different language

The EN 16931 standard defines one data model but allows two XML syntaxes to represent it:

• UBL 2.1 (Universal Business Language) — developed by OASIS, also standardised as ISO/IEC 19845.
• CII (Cross Industry Invoice) — developed by UN/CEFACT.

Think of them as two languages for the same content: the meaning (“invoice date”, “net amount”) is identical, only the XML elements are named differently.

Who uses what?

The XRechnung supports both — the sender decides. ZUGFeRD, by contrast, uses CII only, because the XML there is embedded into a PDF.

Which syntax should you choose?

Since both are equally conformant, there is no “better” choice in a technical sense. Decide based on practice:

• Follow the recipient: some bodies or systems prefer one syntax.
• Follow your software: use the format that your tool produces cleanly.
• When in doubt, UBL, if you send via Peppol.

For the recipient it makes little difference anyway: good software reads both syntaxes and validates both against EN 16931.

Open and check both syntaxes

Whether UBL or CII — you can open the file and display it readably and validate it against EN 16931. The tool detects the syntax automatically, locally in the browser.