BR-01 Specification identifier is required

This is an EN 16931 core rule, so it applies to every CIUS, including XRechnung, Peppol BIS and Factur-X/ZUGFeRD. BT-24 tells the recipient and the validator which specification the invoice claims to follow; the KoSIT validator selects its validation scenario from this value. The error usually appears when an export writes the invoice data but leaves the profile setting empty. For XRechnung, the value must also match the XRechnung URN (BR-DE-21).

Add cbc:CustomizationID in UBL, or rsm:ExchangedDocumentContext/ram:GuidelineSpecifiedDocumentContextParameter/ram:ID in CII, with the identifier of the specification the invoice follows: urn:cen.eu:en16931:2017 for the core standard, urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0 for XRechnung 3.0, or urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0 for Peppol BIS Billing 3.0.