diff --git a/addons/purchase/models/purchase.py b/addons/purchase/models/purchase.py
index 451823e2057..3700a2ad677 100644
--- a/addons/purchase/models/purchase.py
+++ b/addons/purchase/models/purchase.py
@@ -555,13 +555,34 @@ class PurchaseOrderLine(models.Model):
         line = super(PurchaseOrderLine, self).create(values)
         if line.order_id.state == 'purchase':
             line.order_id._create_picking()
+            msg = _("Extra line with %s ") % (line.product_id.display_name,)
+            line.order_id.message_post(body=msg)
         return line
 
     @api.multi
     def write(self, values):
+        orders = False
+        if 'product_qty' in values:
+            changed_lines = self.filtered(lambda x: x.order_id.state == 'purchase')
+            if changed_lines:
+                orders = changed_lines.mapped('order_id')
+                for order in orders:
+                    order_lines = changed_lines.filtered(lambda x: x.order_id == order)
+                    msg = ""
+                    if any([values['product_qty'] < x.product_qty for x in order_lines]):
+                        msg += "<b>" + _('The ordered quantity has been decreased. Do not forget to take it into account on your bills and receipts.') + '</b><br/>'
+                    msg += "<ul>"
+                    for line in order_lines:
+                        msg += "<li> %s:" % (line.product_id.display_name,)
+                        msg += "<br/>" + _("Ordered Quantity") + ": %s -> %s <br/>" % (line.product_qty, float(values['product_qty']),)
+                        if line.product_id.type in ('product', 'consu'):
+                            msg += _("Received Quantity") + ": %s <br/>" % (line.qty_received,)
+                        msg += _("Billed Quantity") + ": %s <br/></li>" % (line.qty_invoiced,)
+                    msg += "</ul>"
+                    order.message_post(body=msg)
         result = super(PurchaseOrderLine, self).write(values)
-        orders = self.filtered(lambda x: x.order_id.state == 'purchase').mapped('order_id')
-        orders._create_picking()
+        if orders:
+            orders._create_picking()
         return result
 
     name = fields.Text(string='Description', required=True)
diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index dda33048a23..b4f8286a959 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -684,16 +684,37 @@ class SaleOrderLine(models.Model):
         line = super(SaleOrderLine, self).create(values)
         if line.state == 'sale':
             line._action_procurement_create()
+            msg = _("Extra line with %s ") % (line.product_id.display_name,)
+            line.order_id.message_post(body=msg)
 
         return line
 
     @api.multi
     def write(self, values):
         lines = False
+        changed_lines = False
         if 'product_uom_qty' in values:
             precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
             lines = self.filtered(
                 lambda r: r.state == 'sale' and float_compare(r.product_uom_qty, values['product_uom_qty'], precision_digits=precision) == -1)
+            changed_lines = self.filtered(
+                lambda r: r.state == 'sale' and float_compare(r.product_uom_qty, values['product_uom_qty'], precision_digits=precision) != 0)
+            if changed_lines:
+                orders = self.mapped('order_id')
+                for order in orders:
+                    order_lines = changed_lines.filtered(lambda x: x.order_id == order)
+                    msg = ""
+                    if any([values['product_uom_qty'] < x.product_uom_qty for x in order_lines]):
+                        msg += "<b>" + _('The ordered quantity has been decreased. Do not forget to take it into account on your invoices and delivery orders.') + '</b>'
+                    msg += "<ul>"
+                    for line in order_lines:
+                        msg += "<li> %s:" % (line.product_id.display_name,)
+                        msg += "<br/>" + _("Ordered Quantity") + ": %s -> %s <br/>" % (line.product_uom_qty, float(values['product_uom_qty']),)
+                        if line.product_id.type in ('consu', 'product'):
+                            msg += _("Delivered Quantity") + ": %s <br/>" % (line.qty_delivered,)
+                        msg += _("Invoiced Quantity") + ": %s <br/>" % (line.qty_invoiced,)
+                    msg += "</ul>"
+                    order.message_post(body=msg)
         result = super(SaleOrderLine, self).write(values)
         if lines:
             lines._action_procurement_create()