Use the InvoiceDocumentReference/ID sub-elements of the BillingReference element.

Element

Element	Description
`Invoice/BillingReference/InvoiceDocumentReference/ID`	Specify the number of the referenced document.

Country Specific Configurations

Netherlands: Invoice Reference
Italy: Invoice Reference Number
Germany: Corrected Invoices
Malaysia: Original e-Invoice Reference
Malaysia: Supplier's Billing Reference Number

Example

<ubl:Invoice>
    <cac:BillingReference>
        <cac:InvoiceDocumentReference>
            <!-- Code omitted for clarity -->
            <cbc:ID>INV22334455</cbc:ID>
            <!-- Code omitted for clarity -->
        </cac:InvoiceDocumentReference>
    </cac:BillingReference>
</ubl:Invoice>