What is EN 16931?
EN 16931 is the European standard that defines the core data of an electronic invoice: seller, buyer, lines, taxes and totals, each with a numbered business term. Formats such as UBL and CII carry that model, so different systems read the same invoice.
Example
Invoice 2026-114 has two lines: 10 chairs at 120.00 and delivery at 50.00, VAT 21% on both. Net is 1,250.00, VAT 262.50 and payable 1,512.50.
In the standard, the invoice number is BT-1, the purchase order reference is BT-13, and the VAT total is BT-110. A UBL file and a CII file hold the same business terms in different XML. Both validate against the same rules.
In Atta
There is one EN 16931 model in the code, with amounts as decimal strings and never floats. Formats are rows in a table, each with its own reader and writer, and a format with no row is refused. Channels, such as Peppol, are separate from formats.
When an invoice is received, Atta links it to a purchase through BT-13, then BT-10, and shows it as that request's invoice row. When it sends one, the payload is stored exactly as it left. Keeping model, format and channel apart means a new country's format is a new row, not a rewrite.
Why it exists
Before the standard, every country and vendor invented its own fields, and each pair of systems needed a mapping. A common semantic model means one mapping per system instead of one per pair. The numbered terms (BT-1, BT-13) are how validators and support teams point at the same field.
Questions
Does EN 16931 cover every country's rules?
It is the common core. Countries add their own extensions, called CIUS, on top.
Related
- What is Peppol?Peppol is an international network for sending structured e-invoices between companies. Definition, how addressing works and a worked example.
- What is PO matching?PO matching links a supplier invoice to the purchase order it belongs to and checks price and quantity agree. Definition with a worked example.
- E-invoicing for purchases: Peppol, XRechnung and Factur-XAtta sends purchase orders over Peppol, receives e-invoices in EN 16931 formats like XRechnung and Factur-X, and links each one to the purchase it names.