diff --git a/models/__init__.py b/models/__init__.py
index 2d759130246b635ba5cb249de9d05600128c84c4..82607947345efb7a0b6ad93be477d00ea55f695c 100644
--- a/models/__init__.py
+++ b/models/__init__.py
@@ -2,4 +2,5 @@
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
 from . import account
+from . import res_users
 from . import sale
diff --git a/models/account.py b/models/account.py
index 93061520fae421bdda63fb2e52cd96238872c248..12f076b7d922119f2db511c3f4e5c2b751b263fa 100644
--- a/models/account.py
+++ b/models/account.py
@@ -1,7 +1,7 @@
 # Copyright 2021 Le Filament (<http://www.le-filament.com>)
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
-from odoo import fields, models, api
+from odoo import fields, models
 
 
 class AccountInvoice(models.Model):
@@ -11,8 +11,13 @@ class AccountInvoice(models.Model):
     # Fields declaration
     # ------------------------------------------------------
     user_second_id = fields.Many2one(
-        'res.users',
-        string='Spécialiste',
+        comodel_name='res.users',
+        string='Spécialiste')
+    user_second_ids = fields.Many2many(
+        comodel_name='res.users',
+        column1='invoice_id',
+        column2='user_id',
+        string='Spécialistes',
         track_visibility='onchange',
         copy=False)
     user_provider_id = fields.Many2one(
diff --git a/models/res_users.py b/models/res_users.py
new file mode 100644
index 0000000000000000000000000000000000000000..d89b863488e4ca2c1323eec43bf8e267a8618d6e
--- /dev/null
+++ b/models/res_users.py
@@ -0,0 +1,24 @@
+# Copyright 2021 Le Filament (<http://www.le-filament.com>)
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
+
+from odoo import fields, models
+
+
+class ResUsers(models.Model):
+    _inherit = "res.users"
+
+    # ------------------------------------------------------
+    # Fields declaration
+    # ------------------------------------------------------
+    order_second_ids = fields.Many2many(
+        comodel_name='sale.order',
+        column1='user_id',
+        column2='order_id',
+        string='Commandes',
+        copy=False)
+    invoice_second_ids = fields.Many2many(
+        comodel_name='account.invoice',
+        column1='user_id',
+        column2='invoice_id',
+        string='Factures',
+        copy=False)
diff --git a/models/sale.py b/models/sale.py
index cfc7324b24901813c94f612a9af3fc86e111d274..2cb962cea66223db07bc14179de9dfb82f153a61 100644
--- a/models/sale.py
+++ b/models/sale.py
@@ -11,8 +11,13 @@ class SaleOrder(models.Model):
     # Fields declaration
     # ------------------------------------------------------
     user_second_id = fields.Many2one(
-        'res.users',
-        string='Spécialiste',
+        comodel_name='res.users',
+        string='Spécialiste')
+    user_second_ids = fields.Many2many(
+        comodel_name='res.users',
+        column1='order_id',
+        column2='user_id',
+        string='Spécialistes',
         track_visibility='onchange',
         copy=False)
     user_provider_id = fields.Many2one(
@@ -52,7 +57,7 @@ class SaleOrder(models.Model):
     def _prepare_invoice(self):
         values = super(SaleOrder, self)._prepare_invoice()
         values.update({
-            'user_second_id': self.user_second_id.id or False,
+            'user_second_ids': [(6, 0, self.user_second_ids.ids)],
             'user_provider_id': self.user_provider_id.id or False,
         })
         return values
diff --git a/views/account_views.xml b/views/account_views.xml
index 4c78300928a3106e8b35534a7275cc22e953e023..b1661fdde8129be4a02adf226155474be387d548 100644
--- a/views/account_views.xml
+++ b/views/account_views.xml
@@ -8,7 +8,7 @@
             <field name="inherit_id" ref="account.invoice_form"/>
             <field name="arch" type="xml">
                 <field name="user_id" position="after">
-                    <field name="user_second_id" options="{'no_create_edit': 1}"/>
+                    <field name="user_second_ids" options="{'no_create_edit': 1}" widget="many2many_tags"/>
                     <field name="user_provider_id" options="{'no_create_edit': 1}"/>
                 </field>
             </field>
diff --git a/views/sale_views.xml b/views/sale_views.xml
index d6c544a536d57b18dcf0fa0b39f037efaa983571..735acdf903bbe545d06306ed049e6a4638a1f17a 100644
--- a/views/sale_views.xml
+++ b/views/sale_views.xml
@@ -8,7 +8,7 @@
             <field name="inherit_id" ref="sale.view_order_form"/>
             <field name="arch" type="xml">
                 <xpath expr="//notebook//page[@name='other_information']//group//group//field[@name='user_id']" position="after">
-                    <field name="user_second_id" options="{'no_create_edit': 1}"/>
+                    <field name="user_second_ids" options="{'no_create_edit': 1}" widget="many2many_tags"/>
                     <field name="user_provider_id" options="{'no_create_edit': 1}"/>
                 </xpath>
             </field>