This document specifies the mapping between the semantic model of an electronic invoice, included in EN16931-1 and the UBL2.1 syntax ( ISO/IEC19845). For each element in the semantic model (including sub-elements or supplementary components such as Identification scheme identifiers) it is defined which element in the syntax is to be used to contain its information contents. Any mismatches between semantics, format, cardinality or structure are indicated.