BR-01: Missing specification identifier
Severity: error
What it means
The invoice does not say which specification/profile it follows (BT-24, Specification identifier).
Most common cause
cbc:CustomizationID (UBL) or GuidelineSpecifiedDocumentContextParameter/ID (CII) is empty or missing from the ERP export.
How to fix it
Set the CustomizationID/GuidelineSpecifiedDocumentContextParameter to the correct profile URN your buyer requires (e.g. the EN16931 or XRechnung URN).