[IBR-070-OM] - A VAT breakdown (IBG-23) with VAT category code (IBT-118) 'O' (Not subject to VAT) MUST NOT have a VAT exemption reason code (IBT-121).
IBR-070-OMubl:Invoice/cac:TaxTotal/cac:TaxSubtotal | cn:CreditNote/cac:TaxTotal/cac:TaxSubtotalnot($vatCategory='O') or not(cac:TaxCategory/cbc:TaxExemptionReasonCode)