[BR-O-10]-A VAT Breakdown (BG-23) with VAT Category code (BT-118) " Not subject to VAT" shall have a VAT exemption reason code (BT-121), meaning " Not subject to VAT" or a VAT exemption reason text (BT-120) " Not subject to VAT" (or the equivalent standard text in another language).
Stored validation assertion
(ram:ExemptionReason) or (ram:ExemptionReasonCode)