[aligned-ibrp-sr-12]-Seller VAT identifier (ibt-031) MUST occur maximum once
aligned-ibrp-sr-12
/ubl:Invoice | /cn:CreditNote
(count(cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme[cac:TaxScheme/upper-case(cbc:ID)='VAT']/cbc:CompanyID) <= 1)