UBL vs CII vs Factur-X: which e-invoice format, and when
Three names, one underlying standard. Here's the difference between UBL, UN/CEFACT CII and Factur-X — and how to know which one to send.
UBL vs CII vs Factur-X: which e-invoice format, and when
These three names cause a lot of confusion because they overlap. The key insight: they all carry the same data — the EN 16931 invoice model. They differ in how that data is written and packaged.
The one-line definitions
- UBL 2.1 — an XML syntax. The format Peppol BIS 3.0 uses. Pure structured
data, no PDF.
- UN/CEFACT CII — a different XML syntax for the same EN 16931 fields.
Common in France/Germany; the XML that lives inside Factur-X/ZUGFeRD.
- Factur-X — not a third syntax but a package: a readable PDF/A-3 with a
CII XML embedded inside it. See Factur-X explained.
So UBL and CII are languages; Factur-X is a hybrid document that speaks CII inside a PDF.
Side by side
| | UBL | CII | Factur-X | |---|---|---|---| | What it is | XML syntax | XML syntax | PDF/A-3 + embedded CII | | Human-readable? | No (XML only) | No (XML only) | Yes (the PDF) | | Machine-readable? | Yes | Yes | Yes (the XML) | | Typical use | Peppol BIS 3.0 | France/Germany national | France, when a PDF copy matters | | Underlying model | EN 16931 | EN 16931 | EN 16931 |
How to know which to send
- Sending over Peppol (Belgium, NL, EU default)? → UBL (Peppol BIS 3.0).
You don't choose per-invoice; the network profile is UBL.
- French domestic B2B? → a France CIUS: UBL or CII, or Factur-X if
you want the human-readable PDF carrier. Your platform resolves the exact document type for the recipient.
- Recipient insists on a visible PDF? → Factur-X.
- Pure system-to-system, no PDF needed? → UBL or CII standalone.
In practice you rarely pick manually — a good tool selects the correct profile for the destination and recipient. What matters is that the data is EN 16931-valid.
The trap to avoid
Don't confuse "a PDF with an XML attached by email" with Factur-X. Factur-X is a specific PDF/A-3 with the CII embedded to spec and the two representations in agreement. A random PDF + loose XML won't validate.
Where Eurobillr fits
Eurobillr models every invoice on EN 16931, then emits the right shape for the destination: UBL for Peppol BIS 3.0 (Belgium and the EU default), and the French CIUS / Factur-X for domestic France — automatically, with a preview of the exact document before you send. You never hand-craft XML or pick a syntax.
Related: Peppol BIS 3.0 explained · EN 16931 explained.