In a Document level allowance (BG-20) where the Document level allowance VAT category code (BT-95) is "Reverse charge" the Document level allowance VAT rate (BT-96) shall be 0 (zero).
cac:AllowanceCharge[cbc:ChargeIndicator=false()]/cac:TaxCategory[normalize-space(cbc:ID)='AE'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT'](xs:decimal(cbc:Percent) = 0)