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

<data inherit_id="account.report_invoice_document" priority="50">
    <div id="partner_vat_address_not_same_as_shipping" position="after">
        <div t-if="o.partner_id.ref_external">Ref: <span t-field="o.partner_id.ref_external"/></div>
    </div>
    <div id="partner_vat_address_same_as_shipping" position="after">
        <div t-if="o.partner_id.ref_external">Ref: <span t-field="o.partner_id.ref_external"/></div>
    </div>
    <div id="partner_vat_no_shipping" position="after">
        <div t-if="o.partner_id.ref_external">Ref: <span t-field="o.partner_id.ref_external"/></div>
    </div>
</data>