diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index 77bd31385cc..4bbb9283081 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -198,6 +198,10 @@ class SaleOrder(models.Model):
     authorized_transaction_ids = fields.Many2many('payment.transaction', compute='_compute_authorized_transaction_ids',
                                                   string='Authorized Transactions', copy=False, readonly=True)
 
+    _sql_constraints = [
+        ('confirmation_date_conditional_required', "CHECK( (state IN ('sale', 'done') AND confirmation_date IS NOT NULL) OR state NOT IN ('sale', 'done') )", "A confirmed sales order requires a confirmation date."),
+    ]
+
     @api.depends('pricelist_id', 'date_order', 'company_id')
     def _compute_currency_rate(self):
         for order in self:
@@ -221,7 +225,7 @@ class SaleOrder(models.Model):
         """
         for order in self:
             dates_list = []
-            confirm_date = fields.Datetime.from_string((order.confirmation_date or order.write_date) if order.state == 'sale' else fields.Datetime.now())
+            confirm_date = fields.Datetime.from_string(order.confirmation_date if order.state in ['sale', 'done'] else fields.Datetime.now())
             for line in order.order_line.filtered(lambda x: x.state != 'cancel' and not x._is_delivery()):
                 dt = confirm_date + timedelta(days=line.customer_lead or 0.0)
                 dates_list.append(dt)
diff --git a/addons/sale/views/sale_views.xml b/addons/sale/views/sale_views.xml
index 23c5895fc08..363fdd21f84 100644
--- a/addons/sale/views/sale_views.xml
+++ b/addons/sale/views/sale_views.xml
@@ -289,7 +289,7 @@
                         </group>
                         <group>
                             <field name="validity_date" attrs="{'invisible': [('state', 'in', ['sale', 'done'])]}"/>
-                            <field name="confirmation_date" attrs="{'invisible': [('state', 'in', ['draft', 'sent', 'cancel'])]}"/>
+                            <field name="confirmation_date" attrs="{'invisible': [('state', 'in', ['draft', 'sent', 'cancel'])], 'required': [('state', 'in', ['sale', 'done'])]}"/>
                             <field name="pricelist_id" groups="product.group_sale_pricelist"/>
                             <field name="currency_id" invisible="1"/>
                             <field name="payment_term_id" options="{'no_create': True}"/>
diff --git a/addons/sale_stock/models/sale_order.py b/addons/sale_stock/models/sale_order.py
index 15054b6507e..6e7106a930c 100644
--- a/addons/sale_stock/models/sale_order.py
+++ b/addons/sale_stock/models/sale_order.py
@@ -48,7 +48,7 @@ class SaleOrder(models.Model):
         super(SaleOrder, self)._compute_expected_date()
         for order in self:
             dates_list = []
-            confirm_date = fields.Datetime.from_string((order.confirmation_date or order.write_date) if order.state == 'sale' else fields.Datetime.now())
+            confirm_date = fields.Datetime.from_string(order.confirmation_date if order.state in ['sale', 'done'] else fields.Datetime.now())
             for line in order.order_line.filtered(lambda x: x.state != 'cancel' and not x._is_delivery()):
                 dt = confirm_date + timedelta(days=line.customer_lead or 0.0)
                 dates_list.append(dt)
@@ -301,7 +301,7 @@ class SaleOrderLine(models.Model):
 
     @api.onchange('product_uom_qty')
     def _onchange_product_uom_qty(self):
-        # When modifying a one2many, _origin doesn't guarantee that its values will be the ones 
+        # When modifying a one2many, _origin doesn't guarantee that its values will be the ones
         # in database. Hence, we need to explicitly read them from there.
         if self._origin:
             product_uom_qty_origin = self._origin.read(["product_uom_qty"])[0]["product_uom_qty"]