[IBR-039-OM] - In Line VAT information (IBG-30) where Invoiced item VAT category code (IBT-151) is 'Exempt', Line Item VAT Amount (BTOM-016) shall be zero.
IBR-039-OMcac:InvoiceLine | cac:CreditNoteLinenot($vatCategory='E') or $lineTaxAmount = 0