A VAT breakdown (BG-23) with VAT Category code (BT-118) "Exempt from VAT" shall have a VAT exemption reason code (BT-121) or a VAT exemption reason text (BT-120).
/*/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[normalize-space(cbc:ID) = 'E'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']exists(cbc:TaxExemptionReason) or exists(cbc:TaxExemptionReasonCode)