The core EN 16931 rules — which fields an invoice has to carry

The BR family is the base layer of EN 16931: it does not check whether your numbers are right, but whether the fields that make a document an invoice under European law are present at all.

59 rules · 59 explained · Rule set v2026-08-31

Why nearly every BR failure has the same cause

These rules almost never fail alone. Map an existing PDF invoice template into XML and the fields that were never visible on paper have no source in the system either — and you get five or ten BR findings at once.

So the fastest route is not to work through them one at a time but to lay the mapping against the mandatory-field list once. The fields that surface are nearly always the same ones: BT-24 (specification identifier), BT-3 (invoice type), BT-5 (currency) and the seller’s tax details.

What these rules do not check

An invoice that passes every BR rule is formally complete and can still be substantively wrong: the wrong tax rate, the wrong description of the supply, the wrong recipient. The BMF letter of 15 October 2025 calls that its own class of error, and no technical check detects it.

The converse also holds: a BR breach matters for VAT only insofar as it touches a mandatory particular. A missing specification identifier makes the document technically unusable and says nothing about the input tax deduction.

All core rules

With the official rule text. Rules with a written explanation carry their cause and fix directly beneath.

NormAPI provides technical validation, not tax or legal advice.