[IBR-054-OM] - In Line VAT information (IBG-30) where Invoiced item VAT category code (IBT-151) is 'Not Subject to VAT', Line Item VAT Amount (BTOM-016) shall be zero.
IBR-054-OMcac:InvoiceLine | cac:CreditNoteLinenot($vatCategory='O') or $lineTaxAmount=0