diff --git a/addons/account/controllers/portal.py b/addons/account/controllers/portal.py
index 4303f972f93..155c38d1a05 100644
--- a/addons/account/controllers/portal.py
+++ b/addons/account/controllers/portal.py
@@ -139,12 +139,14 @@ class PortalAccount(CustomerPortal):
         error, error_message = super(PortalAccount, self).details_form_validate(data)
         # prevent VAT/name change if invoices exist
         partner = request.env['res.users'].browse(request.uid).partner_id
-        invoices = request.env['account.invoice'].sudo().search_count([('partner_id', '=', partner.id), ('state', 'not in', ['draft', 'cancel'])])
-        if invoices:
+        if not partner.can_edit_vat():
             if 'vat' in data and (data['vat'] or False) != (partner.vat or False):
                 error['vat'] = 'error'
                 error_message.append(_('Changing VAT number is not allowed once invoices have been issued for your account. Please contact us directly for this operation.'))
             if 'name' in data and (data['name'] or False) != (partner.name or False):
                 error['name'] = 'error'
                 error_message.append(_('Changing your name is not allowed once invoices have been issued for your account. Please contact us directly for this operation.'))
+            if 'company_name' in data and (data['company_name'] or False) != (partner.company_name or False):
+                error['company_name'] = 'error'
+                error_message.append(_('Changing your company name is not allowed once invoices have been issued for your account. Please contact us directly for this operation.'))
         return error, error_message
diff --git a/addons/account/models/partner.py b/addons/account/models/partner.py
index a1fa22a824c..f28cec604b5 100644
--- a/addons/account/models/partner.py
+++ b/addons/account/models/partner.py
@@ -441,3 +441,15 @@ class ResPartner(models.Model):
         action['domain'] = literal_eval(action['domain'])
         action['domain'].append(('partner_id', 'child_of', self.id))
         return action
+
+    def can_edit_vat(self):
+        can_edit_vat = super(ResPartner, self).can_edit_vat()
+        if not can_edit_vat:
+            return can_edit_vat
+        Invoice = self.env['account.invoice']
+        has_invoice = Invoice.search([
+            ('type', 'in', ['out_invoice', 'out_refund']),
+            ('partner_id', 'child_of', self.commercial_partner_id.id),
+            ('state', 'not in', ['draft', 'cancel'])
+        ], limit=1)
+        return can_edit_vat and not (bool(has_invoice))
diff --git a/addons/portal/controllers/portal.py b/addons/portal/controllers/portal.py
index c12a10ebfaf..ee0d9454567 100644
--- a/addons/portal/controllers/portal.py
+++ b/addons/portal/controllers/portal.py
@@ -198,19 +198,23 @@ class CustomerPortal(Controller):
             error_message.append(_('Invalid Email! Please enter a valid email address.'))
 
         # vat validation
-        partner = request.env["res.partner"]
-        if data.get("vat") and hasattr(partner, "check_vat"):
-            if data.get("country_id"):
-                data["vat"] = request.env["res.partner"].fix_eu_vat_number(int(data.get("country_id")), data.get("vat"))
-            partner_dummy = partner.new({
-                'vat': data['vat'],
-                'country_id': (int(data['country_id'])
-                               if data.get('country_id') else False),
-            })
-            try:
-                partner_dummy.check_vat()
-            except ValidationError:
-                error["vat"] = 'error'
+        partner = request.env.user.partner_id
+        if data.get("vat") and partner and partner.vat != data.get("vat"):
+            if partner.can_edit_vat():
+                if hasattr(partner, "check_vat"):
+                    if data.get("country_id"):
+                        data["vat"] = request.env["res.partner"].fix_eu_vat_number(int(data.get("country_id")), data.get("vat"))
+                    partner_dummy = partner.new({
+                        'vat': data['vat'],
+                        'country_id': (int(data['country_id'])
+                                       if data.get('country_id') else False),
+                    })
+                    try:
+                        partner_dummy.check_vat()
+                    except ValidationError:
+                        error["vat"] = 'error'
+            else:
+                error_message.append(_('Changing VAT number is not allowed once document(s) have been issued for your account. Please contact us directly for this operation.'))
 
         # error message for empty required fields
         if [err for err in error.values() if err == 'missing']:
diff --git a/addons/portal/models/__init__.py b/addons/portal/models/__init__.py
index 320a9e84f38..5e3573d88dc 100644
--- a/addons/portal/models/__init__.py
+++ b/addons/portal/models/__init__.py
@@ -3,4 +3,5 @@
 
 from . import mail_thread
 from . import mail_message
-from . import portal_mixin
\ No newline at end of file
+from . import portal_mixin
+from . import res_partner
diff --git a/addons/portal/models/res_partner.py b/addons/portal/models/res_partner.py
new file mode 100644
index 00000000000..4c8d02943c5
--- /dev/null
+++ b/addons/portal/models/res_partner.py
@@ -0,0 +1,11 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo import models
+
+
+class ResPartner(models.Model):
+    _inherit = 'res.partner'
+
+    def can_edit_vat(self):
+        return True
diff --git a/addons/portal/views/portal_templates.xml b/addons/portal/views/portal_templates.xml
index 64f24c95271..6c21e669fea 100644
--- a/addons/portal/views/portal_templates.xml
+++ b/addons/portal/views/portal_templates.xml
@@ -256,11 +256,11 @@
                             <div t-attf-class="form-group #{error.get('company_name') and 'has-error' or ''} col-lg-6">
                                 <label class="control-label label-optional" for="company_name">Company Name</label>
                                 <p t-if="partner.commercial_partner_id.is_company" class="form-control" t-esc="partner.commercial_company_name"/>
-                                <input t-else="" type="text" name="company_name" class="form-control" t-att-value="company_name or partner.company_name"/>
+                                <input t-else="" type="text" name="company_name" class="form-control" t-att-value="company_name or partner.company_name" t-att-readonly="None if partner.can_edit_vat() else '1'" t-att-title="None if partner.can_edit_vat() else 'Changing company name is not allowed once document(s) have been issued for your account. Please contact us directly for this operation.'"/>
                             </div>
-                            <div t-if="has_check_vat" t-attf-class="form-group #{error.get('vat') and 'has-error' or ''} col-lg-6">
+                            <div 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" />
+                                <input type="text" name="vat" class="form-control" t-att-value="vat or partner.vat" t-att-readonly="None if partner.can_edit_vat() else '1'" t-att-title="None if partner.can_edit_vat() else 'Changing VAT number is not allowed once document(s) have been issued for your account. Please contact us directly for this operation.'" />
                             </div>
 
                             <div class="clearfix" />
diff --git a/addons/sale/models/res_partner.py b/addons/sale/models/res_partner.py
index c77bb965620..26039c1f2f6 100644
--- a/addons/sale/models/res_partner.py
+++ b/addons/sale/models/res_partner.py
@@ -25,3 +25,14 @@ class ResPartner(models.Model):
             partner_ids = [partner.id] + item.get('child_ids')
             # then we can sum for all the partner's child
             partner.sale_order_count = sum(mapped_data.get(child, 0) for child in partner_ids)
+
+    def can_edit_vat(self):
+        can_edit_vat = super(ResPartner, self).can_edit_vat()
+        if not can_edit_vat:
+            return can_edit_vat
+        SaleOrder = self.env['sale.order']
+        has_so = SaleOrder.search([
+            ('partner_id', 'child_of', self.commercial_partner_id.id),
+            ('state', 'in', ['sent', 'sale', 'done'])
+        ], limit=1)
+        return can_edit_vat and not bool(has_so)
diff --git a/addons/website_sale/controllers/main.py b/addons/website_sale/controllers/main.py
index 9ef132937eb..20d08265b24 100644
--- a/addons/website_sale/controllers/main.py
+++ b/addons/website_sale/controllers/main.py
@@ -590,6 +590,7 @@ class WebsiteSale(http.Controller):
             return redirection
 
         mode = (False, False)
+        can_edit_vat = False
         def_country_id = order.partner_id.country_id
         values, errors = {}, {}
 
@@ -598,6 +599,7 @@ class WebsiteSale(http.Controller):
         # IF PUBLIC ORDER
         if order.partner_id.id == request.website.user_id.sudo().partner_id.id:
             mode = ('new', 'billing')
+            can_edit_vat = True
             country_code = request.session['geoip'].get('country_code')
             if country_code:
                 def_country_id = request.env['res.country'].search([('code', '=', country_code)], limit=1)
@@ -608,6 +610,7 @@ class WebsiteSale(http.Controller):
             if partner_id > 0:
                 if partner_id == order.partner_id.id:
                     mode = ('edit', 'billing')
+                    can_edit_vat = order.partner_id.can_edit_vat()
                 else:
                     shippings = Partner.search([('id', 'child_of', order.partner_id.commercial_partner_id.ids)])
                     if partner_id in shippings.mapped('id'):
@@ -651,6 +654,7 @@ class WebsiteSale(http.Controller):
             'partner_id': partner_id,
             'mode': mode,
             'checkout': values,
+            'can_edit_vat': can_edit_vat,
             'country': country,
             'countries': country.get_website_sale_countries(mode=mode[1]),
             "states": country.get_website_sale_states(mode=mode[1]),
diff --git a/addons/website_sale/views/templates.xml b/addons/website_sale/views/templates.xml
index fae39820b64..e008c155968 100644
--- a/addons/website_sale/views/templates.xml
+++ b/addons/website_sale/views/templates.xml
@@ -1161,14 +1161,14 @@
                                         <input type="tel" name="phone" class="form-control" t-att-value="'phone' in checkout and checkout['phone']" />
                                     </div>
                                     <div class="clearfix" />
-                                    <t t-if="mode == ('new', 'billing')">
+                                    <t t-if="mode == ('new', 'billing') or (mode == ('edit', 'billing') and (can_edit_vat or 'vat' in checkout and checkout['vat']))">
                                         <div t-attf-class="form-group #{error.get('company_name') and 'has-error' or ''} col-md-6">
                                             <label class="control-label font-weight-normal label-optional" for="company_name">Company Name</label>
-                                            <input type="text" name="company_name" class="form-control" t-att-value="'company_name' in checkout and checkout['company_name']" />
+                                            <input type="text" name="company_name" class="form-control" t-att-value="'company_name' in checkout and checkout['company_name']" t-att-readonly="'1' if 'vat' in checkout and checkout['vat'] and not can_edit_vat else None" t-att-title="'Changing company name is not allowed once document(s) have been issued for your account. Please contact us directly for this operation.' if 'vat' in checkout and checkout['vat'] and not can_edit_vat else None" />
                                         </div>
                                         <div t-attf-class="form-group #{error.get('vat') and 'has-error' or ''} col-md-6 div_vat">
                                             <label class="control-label font-weight-normal label-optional" for="vat">TIN / VAT </label>
-                                            <input type="text" name="vat" class="form-control" t-att-value="'vat' in checkout and checkout['vat']" />
+                                            <input type="text" name="vat" class="form-control" t-att-value="'vat' in checkout and checkout['vat']" t-att-readonly="'1' if 'vat' in checkout and checkout['vat'] and not can_edit_vat else None" t-att-title="'Changing VAT number is not allowed once document(s) have been issued for your account. Please contact us directly for this operation.' if 'vat' in checkout and checkout['vat'] and not can_edit_vat else None" />
                                         </div>
                                     </t>
                                     <div class="clearfix" />