[ibr-09-ng]-Document level charge (IBG-21) with Document level charge VAT category code (IBT-102) as 'Exempt from VAT' MUST have a Document level charge VAT exemption reason code (IBT-198).
ibr-09-ngcac:AllowanceCharge[cbc:ChargeIndicator = true()]not(cac:TaxCategory/cbc:ID = "E" and not(exists(cbc:AllowanceChargeReasonCode)))