[UBL-SR-13-GST-SG]-Seller tax registration shall occur maximum once
UBL-SR-13-GST-SG
/ubl:Invoice | /cn:CreditNote
(count(cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme[cac:TaxScheme/cbc:ID!='GST']/cbc:ID) <= 1)