Use the OrderLineReference/ID subelement of the InvoiceLine element to model this information.

More information is provided in the Sales and Order References topic.

Example

<Invoice>
    <!-- code omitted for clarity -->
    <cac:InvoiceLine>
        <!-- code omitted for clarity -->
        <cac:OrderLineReference>
            <cbc:LineID>120</cbc:LineID>
            <cac:OrderReference>
                <cbc:ID>PO12345</cbc:ID>
            </cac:OrderReference>
        </cac:OrderLineReference>
        <!-- code omitted for clarity -->
    </cac:InvoiceLine>
</Invoice>