An Invoice that contains a Document level allowance (BG-20) where the Document level allowance VAT category code (BT-95) is "Standard rated" shall contain the Seller VAT Identifier (BT-31), the Seller tax registration identifier (BT-32) and/or the Seller tax representative VAT identifier (BT-63).
/ubl:Invoice | /cn:CreditNote(exists(//cac:AllowanceCharge[cbc:ChargeIndicator=false()]/cac:TaxCategory[normalize-space(cbc:ID)='S'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']) and (exists(//cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme/cbc:CompanyID) or exists(//cac:TaxRepresentativeParty/cac:PartyTaxScheme[cac:TaxScheme/(normalize-space(upper-case(cbc:ID)) = 'VAT')]/cbc:CompanyID))) or not(exists(//cac:AllowanceCharge[cbc:ChargeIndicator=false()]/cac:TaxCategory[normalize-space(cbc:ID)='S'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']))