Odoo-Build/snippets/account.report_invoice_document.show_parent_partner_reference.xml

<?xml version="1.0"?>
<data inherit_id="account.report_invoice_document" priority="50">
    <p t-field="o.partner_id.ref" position="replace">
        <p class="m-0" t-esc="o.partner_id.ref or o.partner_id.parent_id.ref"/>
    </p>
    <div t-if="o.partner_id.ref" position="attributes">
        <attribute name="t-if">o.partner_id.ref or o.partner_id.parent_id.ref</attribute>
    </div>
</data>