Reference · EN 16931

UBL 2.1 and CII D16B: two syntaxes for one invoice

EN 16931 defines what an invoice means; the file format used to write it down is a separate choice. The same invoice can be written in two different XML syntaxes and still be the same invoice.

EN 16931 defines what an invoice means: a list of business terms (BT-) and business term groups (BG-) with defined cardinality and defined relationships between them. It does not define the XML. The standard is expressed in two syntaxes, and a conforming invoice may be written in either.

What each one is

OASIS UBL 2.1 (Universal Business Language) is an OASIS standard whose invoice document is one of a family of business documents sharing common component definitions. UN/CEFACT CII D16B (Cross Industry Invoice) comes from the United Nations Centre for Trade Facilitation and Electronic Business, and its data structures derive from the UN/CEFACT Core Component Library.

Which one should you send?

The receiver decides which syntax to use. The sender has no say in it. A receiving system implements one syntax or both, and which to send is a property of who you are invoicing rather than a preference. This is why producing only one of the two is a limitation worth knowing about in any tool you use.

EUInvoice issues the UBL 2.1 document as the stored original, and makes the same invoice available as a CII D16B rendition. Both are generated from the same underlying invoice record, so they describe the same document rather than two separately edited files.

What this does not cover

Choosing a syntax is not the same as choosing how a document reaches its recipient. Transmission over the Peppol network, Poland's KSeF or France's Chorus Pro / PPF are separate questions with separate requirements, and EUInvoice does not transmit over any of them. This article also does not cover national CIUS or extension specifications, which narrow EN 16931 further for a particular country or sector.