diff --git a/addons/portal/views/portal_templates.xml b/addons/portal/views/portal_templates.xml
index 193c1fdce18..4108a2006b9 100644
--- a/addons/portal/views/portal_templates.xml
+++ b/addons/portal/views/portal_templates.xml
@@ -279,7 +279,8 @@
                             </div>
                             <div t-if="has_check_vat" t-attf-class="form-group #{error.get('vat') and 'has-error' or ''} col-lg-6">
                                 <label class="control-label label-optional" for="vat">VAT Number</label>
-                                <input type="text" name="vat" class="form-control" t-att-value="vat or partner.vat" />
+                                <!-- DO NOT FORWARD-PORT! ONLY FOR v11 -->
+                                <input type="text" name="vat" class="form-control" t-att-value="vat or partner.vat" t-att-readonly="'1' if partner.parent_id else None" />
                             </div>
 
                             <div class="clearfix" />