Representing taxable freight charges in an Invoice

Hi all,
    how is freight typically represented in an Invoice? I want to 
represent freight costs which may or may not attract 10% GST.

E.g:
    <cac:AllowanceCharge>
        <cbc:ChargeIndicator>true</cbc:ChargeIndicator>
        <cbc:AllowanceChargeReason>Freight with 
GST</cbc:AllowanceChargeReason>
        <cbc:Amount currencyID="AUD">10.00</cbc:Amount>
        <cac:TaxTotal>
            <cbc:TaxAmount currencyID="AUD">1.00</cbc:TaxAmount>
        </cac:TaxTotal>
    </cac:AllowanceCharge>
    <cac:AllowanceCharge>
        <cbc:ChargeIndicator>true</cbc:ChargeIndicator>
        <cbc:AllowanceChargeReason>Freight without 
GST</cbc:AllowanceChargeReason>
        <cbc:Amount currencyID="AUD">50.00</cbc:Amount>
    </cac:AllowanceCharge>

I'm assuming that the AllowanceCharge/Amount and 
Invoice/LegalMonetaryTotal/ChargeTotalAmount exclude tax.
Is this valid?

Thanks,

Tim