[IBR-093-OM] - If Document level allowance TAX category code (IBT-095) is 'O', Document level allowance TAX rate (IBT-096) MUST not be present.
IBR-093-OMubl:Invoice/cac:AllowanceCharge[cbc:ChargeIndicator = 'false'] | cn:CreditNote/cac:AllowanceCharge[cbc:ChargeIndicator = 'false']not($cat='O') or not(cac:TaxCategory/cbc:Percent)