You use different elements for different references.

Elements

Order and Billing References

Use the following subelements of the DocumentReference element to model order and billing references:

Element	Description
`Invoice/InvoiceLine/DocumentReference/ID`	Specify the document number.
`Invoice/InvoiceLine/DocumentReference/ID @schemeID`	Use one of the allowed values.

Commitment Document (Número do compromisso)

Use the DocumentReferenceExtension (Extn) Extension to model the Commitment Document (Número do compromisso):

Element	Description
Document Reference Extension Group (`DocumentReference/UBLExtensions/UBLExtension/ExtensionContent/ DocumentReferenceExtension/`)	Groups extended document reference information.
Line ID (`DocumentReference/UBLExtensions/UBLExtension/ExtensionContent/ DocumentReferenceExtension/LineID`)	The line in the Commitment Document that you are referencing.
ID (`Invoice/InvoiceLine/DocumentReference/ID`)	Specify the referenced document's ID.
Scheme Identifier (`Invoice/InvoiceLine/DocumentReference/ID @schemeID`)	Use `VRBL:PT:COMMITMENT`.

Restrictions

You must use one of the following values for the @schemeID attribute:
If you are modelling a reference to the Commitment Document Number of the Commitment Document (Número do compromisso), you need to use the DocumentReferenceExtension. You must add a DocumentReference element that contains the reference. You must also specify VRBL:PT:COMMITMENT in the @schemeID attribute.

Code	Description
`CT`	Order Number
`IV`	Billing reference number
`VRBL:PT:COMMITMENT`	Commitment Document Number (Número do compromisso)

Example

Order and Billing References

The following example shows references to an order and a billing reference:

<ubl:Invoice>
    <!-- Code omitted for clarity -->
    <cac:InvoiceLine>
        <!-- Code omitted for clarity -->
        <cac:DocumentReference>
            <cbc:ID schemeID="CT">CT987654</cbc:ID>
        </cac:DocumentReference>
        <cac:DocumentReference>
            <cbc:ID schemeID="IV">INV987654</cbc:ID>
        </cac:DocumentReference>
        <!-- Code omitted for clarity -->

Commitment Document (Número do compromisso)

The following example shows a reference to the Commitment Document (Número do compromisso):

 <!-- Code omitted for clarity -->
        <cac:DocumentReference>
            <cec:UBLExtensions>
                <cec:UBLExtension>
                    <cec:ExtensionContent>
                        <vrbl:DocumentReferenceExtension>
                            <cbc:LineID>01</cbc:LineID>
                        </vrbl:DocumentReferenceExtension>
                    </cec:ExtensionContent>
                </cec:UBLExtension>
            </cec:UBLExtensions>
            <cbc:ID schemeID="VRBL:PT:COMMITMENT">12345678</cbc:ID>
            <cbc:IssueDate>2024-05-02</cbc:IssueDate>
        </cac:DocumentReference>
        <!-- Code omitted for clarity -->
    </cac:InvoiceLine>
    <!-- Code omitted for clarity -->
</ubl:Invoice>