BR-21 — Missing line identifier

What it means

Each invoice line must have an identifier (a line number). This number lets you unambiguously refer to a specific line, e.g. in corrections or credit notes.

How to fix it

Check that each InvoiceLine has an ID element filled in with a number unique within the invoice (usually 1, 2, 3...).

Example

Wrong: the line has no ID element. Correct: <cac:InvoiceLine><cbc:ID>1</cbc:ID>...</cac:InvoiceLine>.