diff --git a/admin/tool/monitor/classes/eventobservers.php b/admin/tool/monitor/classes/eventobservers.php
index 2ffc4fd5631..3918a7dd32f 100644
--- a/admin/tool/monitor/classes/eventobservers.php
+++ b/admin/tool/monitor/classes/eventobservers.php
@@ -129,6 +129,7 @@ class eventobservers {
         $select = "SELECT COUNT(id) FROM {tool_monitor_events} ";
         $now = time();
         $messagestosend = array();
+        $allsubids = array();
 
         // Let us now process the events and check for subscriptions.
         foreach ($events as $eventobj) {
@@ -136,6 +137,7 @@ class eventobservers {
             $idstosend = array();
             foreach ($subscriptions as $subscription) {
                 $starttime = $now - $subscription->timewindow;
+                $starttime = ($starttime > $subscription->lastnotificationsent) ? $starttime : $subscription->lastnotificationsent;
                 if ($subscription->courseid == 0) {
                     // Site level subscription. Count all events.
                     $where = "eventname = :eventname AND timecreated >  :starttime";
@@ -188,9 +190,18 @@ class eventobservers {
             }
             if (!empty($idstosend)) {
                 $messagestosend[] = array('subscriptionids' => $idstosend, 'event' => $eventobj);
+                $allsubids = array_merge($allsubids, $idstosend);
             }
         }
 
+        if (!empty($allsubids)) {
+            // Update the last trigger flag.
+            list($sql, $params) = $DB->get_in_or_equal($allsubids, SQL_PARAMS_NAMED);
+            $params['now'] = $now;
+            $sql = "UPDATE {tool_monitor_subscriptions} SET lastnotificationsent = :now WHERE id $sql";
+            $DB->execute($sql, $params);
+        }
+
         // Schedule a task to send notification.
         if (!empty($messagestosend)) {
             $adhocktask = new notification_task();
diff --git a/admin/tool/monitor/db/install.xml b/admin/tool/monitor/db/install.xml
index 39d2bb94ef7..7729199f1b8 100644
--- a/admin/tool/monitor/db/install.xml
+++ b/admin/tool/monitor/db/install.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<XMLDB PATH="tool/monitor/db" VERSION="20140708" COMMENT="XMLDB file for Moodle tool/monitor"
+<XMLDB PATH="tool/monitor/db" VERSION="20141103" COMMENT="XMLDB file for Moodle tool/monitor"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="../../../lib/xmldb/xmldb.xsd"
 >
@@ -37,6 +37,7 @@
         <FIELD NAME="cmid" TYPE="int" LENGTH="10" NOTNULL="true" SEQUENCE="false" COMMENT="Course module id"/>
         <FIELD NAME="userid" TYPE="int" LENGTH="10" NOTNULL="true" SEQUENCE="false" COMMENT="User id of the subscriber"/>
         <FIELD NAME="timecreated" TYPE="int" LENGTH="10" NOTNULL="true" SEQUENCE="false" COMMENT="Timestamp of when this subscription was created"/>
+        <FIELD NAME="lastnotificationsent" TYPE="int" LENGTH="10" NOTNULL="true" DEFAULT="0" SEQUENCE="false" COMMENT="Timestamp of the time when a notification was last sent for this subscription."/>
       </FIELDS>
       <KEYS>
         <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
diff --git a/admin/tool/monitor/db/upgrade.php b/admin/tool/monitor/db/upgrade.php
new file mode 100644
index 00000000000..59f0e869fca
--- /dev/null
+++ b/admin/tool/monitor/db/upgrade.php
@@ -0,0 +1,54 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Upgrade scirpt for tool_monitor.
+ *
+ * @package    tool_monitor
+ * @copyright  2014 onwards Ankit Agarwal <ankit.agrr@gmail.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Upgrade the plugin.
+ *
+ * @param int $oldversion
+ * @return bool always true
+ */
+function xmldb_tool_monitor_upgrade($oldversion) {
+    global $DB;
+
+    $dbman = $DB->get_manager();
+
+    if ($oldversion < 2014102000) {
+
+        // Define field lastnotificationsent to be added to tool_monitor_subscriptions.
+        $table = new xmldb_table('tool_monitor_subscriptions');
+        $field = new xmldb_field('lastnotificationsent', XMLDB_TYPE_INTEGER, '10', null, XMLDB_NOTNULL, null, '0', 'timecreated');
+
+        // Conditionally launch add field lastnotificationsent.
+        if (!$dbman->field_exists($table, $field)) {
+            $dbman->add_field($table, $field);
+        }
+
+        // Monitor savepoint reached.
+        upgrade_plugin_savepoint(true, 2014102000, 'tool', 'monitor');
+    }
+
+    return true;
+}
diff --git a/admin/tool/monitor/tests/eventobservers_test.php b/admin/tool/monitor/tests/eventobservers_test.php
index 4e601835ec5..f9d0ed0282f 100644
--- a/admin/tool/monitor/tests/eventobservers_test.php
+++ b/admin/tool/monitor/tests/eventobservers_test.php
@@ -266,6 +266,53 @@ class tool_monitor_eventobservers_testcase extends advanced_testcase {
         $this->verify_processed_data($msgsink);
     }
 
+    /**
+     * Test that same events are not used twice to calculate conditions for a single subscription.
+     */
+    public function test_multiple_notification_not_sent() {
+        global $USER;
+
+        $this->resetAfterTest();
+        $this->setAdminUser();
+        $messagesink = $this->redirectMessages();
+
+        // Generate data.
+        $course = $this->getDataGenerator()->create_course();
+        $toolgenerator = $this->getDataGenerator()->get_plugin_generator('tool_monitor');
+
+        $rulerecord = new stdClass();
+        $rulerecord->courseid = $course->id;
+        $rulerecord->eventname = '\mod_book\event\course_module_instance_list_viewed';
+        $rulerecord->frequency = 5;
+
+        $rule = $toolgenerator->create_rule($rulerecord);
+
+        $subrecord = new stdClass();
+        $subrecord->courseid = $course->id;
+        $subrecord->ruleid = $rule->id;
+        $subrecord->userid = $USER->id;
+        $toolgenerator->create_subscription($subrecord);
+
+        for ($i = 0; $i < 7; $i++) {
+            // Now let us trigger 7 instances of the event.
+            $event = \mod_book\event\course_module_instance_list_viewed::create_from_course($course);
+            $event->trigger();
+            sleep(1); // Add a second delay, to prevent time collisions.
+        }
+        $this->run_adhock_tasks();
+        $messages = $messagesink->get_messages();
+        $this->assertCount(1, $messages); // There should be only one message not 3.
+        for ($i = 0; $i < 3; $i++) {
+            // Now let us trigger 5 more instances of the event.
+            $event = \mod_book\event\course_module_instance_list_viewed::create_from_course($course);
+            $event->trigger();
+        }
+
+        $this->run_adhock_tasks();
+        $messages = $messagesink->get_messages();
+        $this->assertCount(2, $messages); // There should be two messages now.
+    }
+
     /**
      * Run adhoc tasks.
      */
diff --git a/admin/tool/monitor/version.php b/admin/tool/monitor/version.php
index b8150b03136..9231910cfdc 100644
--- a/admin/tool/monitor/version.php
+++ b/admin/tool/monitor/version.php
@@ -26,6 +26,6 @@
 
 defined('MOODLE_INTERNAL') || die;
 
-$plugin->version   = 2014061901;       // The current plugin version (Date: YYYYMMDDXX).
+$plugin->version   = 2014102000;       // The current plugin version (Date: YYYYMMDDXX).
 $plugin->requires  = 2014061900;       // Requires this Moodle version.
 $plugin->component = 'tool_monitor'; // Full name of the plugin (used for diagnostics).