An Invoice that contains a VAT breakdown group (BG-23) with a VAT category code (BT-118) "Not subject to VAT" shall not contain other VAT breakdown groups (BG-23).
/ubl:Invoice | /cn:CreditNote(exists(cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'O']) and count(cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[normalize-space(cbc:ID) != 'O'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']) = 0) or not(cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'O'])