[IBR-012-OM] - Deliver to country code (IBT-080) must not be 'OM' if invoice transaction type (BTOM-001) is export invoice (XXXXXX1XXXXXXXXXXXXX) and atleast one VAT exemption reason code (IBT-121) is 'Export of service (VATZR-OM-09)'.
IBR-012-OMubl:Invoice | cn:CreditNotenot($isExport and $lines//cbc:TaxExemptionReasonCode = 'VATZR-OM-09') or cac:Delivery/cac:DeliveryLocation/cac:Address/cac:Country/cbc:IdentificationCode != 'OM'