[BR-56-GST-SG]-Each Seller tax representative party (BG-11) shall have a Seller tax representative GST identifier (BT-63-GST).
BR-56-GST-SG
cac:TaxRepresentativeParty
exists(cac:PartyTaxScheme[cac:TaxScheme/cbc:ID = 'GST']/cbc:CompanyID)