Message

Australian Business Number (ABN) MUST be stated in the correct format.

Context
cbc:EndpointID[@schemeID = '0151'] | cac:PartyIdentification/cbc:ID[@schemeID = '0151'] | cbc:CompanyID[@schemeID = '0151']
Test
matches(normalize-space(), '^[0-9]{11}$') and u:abn(normalize-space())