You can add additional information in the following format:

#{Code}#{Note}

Where:

{Code} is a code from the UNTDID 4451 list here.
{Note} is your note text.

More information about notes is provided in the Invoice Notes topic.

Example

<Invoice>
    <!-- code omitted for clarity -->
    <!-- ABN = Accounting information -->
    <cbc:InvoiceNote>#ABN#This is an important accounting information.</cbc:InvoiceNote>
    <!-- code omitted for clarity -->
</Invoice>