UBL vs. CII: which e-invoice syntax should you use?

EN 16931 allows two XML syntaxes: OASIS UBL 2.1 and UN/CEFACT Cross Industry Invoice (CII) D16B. Both carry the same business terms, so choosing between them is mostly about your network and your customers.

At a glance

• UBL — root element Invoice or CreditNote; dates as YYYY-MM-DD; used by Peppol BIS 3.0 and XRechnung UBL.
• CII — root element rsm:CrossIndustryInvoice; dates as udt:DateTimeString format 102 (YYYYMMDD); used by Factur-X, ZUGFeRD and XRechnung CII.
• UBL has separate documents for invoices and credit notes; CII uses one document with a type code.
• CII groups data into agreement, delivery and settlement blocks; UBL keeps parties and totals at document level.

Which one should I send?

• Sending via Peppol → UBL (Peppol BIS 3.0).
• Customers want a readable PDF → Factur-X / ZUGFeRD (CII inside a PDF).
• German public sector → XRechnung, either syntax.
• France → any of Factur-X, UBL or CII through your plateforme agréée.

Converting

Because both syntaxes map onto the same semantic model, conversion is lossless for EN 16931 core data. InvoiceVerify's Factur-X → UBL converter reads CII, maps it to the business terms and writes a Peppol BIS 3.0 UBL invoice that is validated immediately.