EN 16931: the European e-invoicing standard

A common meaning for invoice data

EN 16931 is the European standard for the core of an electronic invoice. It does not describe a file format. It describes meaning: which pieces of information an invoice carries, how they relate to each other and which are mandatory. Each piece of information is a numbered business term, such as the invoice number, the issue date or the seller's name, and related terms are grouped into business groups, like the seller or an invoice line.

Because the meaning is fixed, software from different vendors can read each other's invoices without guessing what a field represents.

Syntaxes: how the meaning becomes a file

To exchange real invoices, the semantic model has to be written in a concrete syntax. The standard family names two XML syntaxes that every compliant solution is expected to support: UBL and UN/CEFACT Cross Industry Invoice, usually called CII. The same invoice can be expressed in either one, and a correct conversion between them loses no information that the standard defines.

CIUS profiles and the Peppol BIS

A Core Invoice Usage Specification, or CIUS, narrows the standard for a community, a country or a network. Peppol BIS Billing 3.0 is such a profile: it uses the EN 16931 model, tightens some optional items into mandatory ones and adds rules specific to the Peppol network. An invoice that satisfies the profile also satisfies the underlying standard, but not every standard-conformant invoice satisfies the profile.

Business rules

The standard comes with business rules that an invoice must satisfy beyond just being well-formed XML. Some rules check that mandatory items are present, others check arithmetic, for example that the payable amount equals the tax-inclusive total minus prepayments, and others check consistency between the tax category and the exemption reason. These rules are published as machine-checkable artefacts, which is how validators work.

Fiscalane implements a documented subset of these rules in its pre-flight check. Passing it is a strong signal but is not a certification, and the complete official artefacts remain the authority.