diff --git a/addons/purchase/models/purchase.py b/addons/purchase/models/purchase.py
index d44daaef66e..1861b63588b 100644
--- a/addons/purchase/models/purchase.py
+++ b/addons/purchase/models/purchase.py
@@ -199,6 +199,21 @@ class PurchaseOrder(models.Model):
             vals['name'] = self.env['ir.sequence'].next_by_code('purchase.order') or '/'
         return super(PurchaseOrder, self).create(vals)
 
+    def write(self, vals):
+        if vals.get('order_line') and self.state == 'purchase':
+            for order in self:
+                pre_order_line_qty = {order_line: order_line.product_qty for order_line in order.mapped('order_line')}
+        res = super(PurchaseOrder, self).write(vals)
+        if vals.get('order_line') and self.state == 'purchase':
+            for order in self:
+                to_log = {}
+                for order_line in order.order_line:
+                    if pre_order_line_qty.get(order_line, False) and float_compare(pre_order_line_qty[order_line], order_line.product_qty, precision_rounding=order_line.product_uom.rounding) > 0:
+                        to_log[order_line] = (order_line.product_qty, pre_order_line_qty[order_line])
+                if to_log:
+                    order._log_decrease_ordered_quantity(to_log)
+        return res
+
     @api.multi
     def unlink(self):
         for order in self:
@@ -471,6 +486,41 @@ class PurchaseOrder(models.Model):
                 except AccessError:  # no write access rights -> just ignore
                     break
 
+    def _log_decrease_ordered_quantity(self, purchase_order_lines_quantities):
+
+        def _keys_in_sorted(move):
+            """ sort by picking and the responsible for the product the
+            move.
+            """
+            return (move.picking_id.id, move.product_id.responsible_id.id)
+
+        def _keys_in_groupby(move):
+            """ group by picking and the responsible for the product the
+            move.
+            """
+            return (move.picking_id, move.product_id.responsible_id)
+
+        def _render_note_exception_quantity_po(order_exceptions):
+            order_line_ids = self.env['purchase.order.line'].browse([order_line.id for order in order_exceptions.values() for order_line in order[0]])
+            purchase_order_ids = order_line_ids.mapped('order_id')
+            move_ids = self.env['stock.move'].concat(*rendering_context.keys())
+            impacted_pickings = move_ids.mapped('picking_id')._get_impacted_pickings(move_ids) - move_ids.mapped('picking_id')
+            values = {
+                'purchase_order_ids': purchase_order_ids,
+                'order_exceptions': order_exceptions.values(),
+                'impacted_pickings': impacted_pickings,
+            }
+            return self.env.ref('purchase.exception_on_po').render(values=values)
+
+        documents = self.env['stock.picking']._log_activity_get_documents(purchase_order_lines_quantities, 'move_ids', 'DOWN', _keys_in_sorted, _keys_in_groupby)
+        filtered_documents = {}
+        for (parent, responsible), rendering_context in documents.items():
+            if parent._name == 'stock.picking':
+                if parent.state == 'cancel':
+                    continue
+            filtered_documents[(parent, responsible)] = rendering_context
+        self.env['stock.picking']._log_activity(_render_note_exception_quantity_po, filtered_documents)
+
     @api.multi
     def action_view_picking(self):
         '''
diff --git a/addons/purchase/views/purchase_template.xml b/addons/purchase/views/purchase_template.xml
index 08ab27846d5..71d77830d6c 100644
--- a/addons/purchase/views/purchase_template.xml
+++ b/addons/purchase/views/purchase_template.xml
@@ -14,4 +14,32 @@
             </ul>
         </div>
     </template>
+
+    <template id="exception_on_po">
+        <div class="alert alert-warning"> 
+          Exception(s) occurred on the purchase order(s):
+          <t t-foreach="purchase_order_ids" t-as="purchase_order">
+              <a href="#" data-oe-model="purchase.order" t-att-data-oe-id="purchase_order.id"><t t-esc="purchase_order.name"/></a>.
+          </t>
+          Manual actions may be needed.
+          <div class="mt16">
+              <p>Exception(s):</p>
+              <ul t-foreach="order_exceptions" t-as="exception">
+                  <li>
+                      <t t-set="order_line" t-value="exception[0]"/>
+                      <t t-set="new_qty" t-value="exception[1][0]"/>
+                      <t t-set="old_qty" t-value="exception[1][1]"/>
+                      <t t-esc="new_qty"/> <t t-esc="order_line.product_uom.name"/> of <t t-esc="order_line.product_id.name"/>
+                      ordered instead of <t t-esc="old_qty"/> <t t-esc="order_line.product_uom.name"/>
+                  </li>
+              </ul>
+          </div>
+          <div class="mt16" t-if="impacted_pickings">
+              <p>Next transfer(s) impacted:</p>
+              <ul t-foreach="impacted_pickings" t-as="picking">
+                  <li><a href="#" data-oe-model="stock.picking" t-att-data-oe-id="picking.id"><t t-esc="picking.name"/></a></li>
+              </ul>
+          </div>
+        </div>
+    </template>
 </odoo>