BR-02
EN 16931
FATAL
Every invoice must have an Invoice number (BT-1, cbc:ID). It is the primary key of the document - validators reject the file outright when it is missing or empty.
How to fix it
- Add
cbc:IDwith your invoice number, e.g.INV-2026-0042. - Keep it unique per seller - duplicates cause rejections downstream, not here.
- Do not confuse it with the buyer reference (BT-10) or order reference (BT-13).
Official rule text
An Invoice shall have an Invoice number (BT-1).
Developers also reach this page searching for an “invoice validation error”, an “e-invoice rejected” message, or how to fix a failed EN 16931 compliance check — it's the same issue, explained above.
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