[UBL-SR-15]-Buyer name shall occur maximum once
UBL-SR-15
pxs-taxdata:TaxData/pxs-taxdata:ReportedTransaction/pxs-taxdata:ReportedDocument
(count(cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cbc:RegistrationName) <= 1)