[IBR-094-OM] - If Document level allowance TAX category code (IBT-095) is 'Z', Document level allowance TAX rate (IBT-096) MUST be 0.
IBR-094-OMubl:Invoice/cac:AllowanceCharge[cbc:ChargeIndicator = 'false'] | cn:CreditNote/cac:AllowanceCharge[cbc:ChargeIndicator = 'false']not($cat='Z') or (cac:TaxCategory/cbc:Percent castable as xs:decimal and xs:decimal(cac:TaxCategory/cbc:Percent) = 0)