diff --git a/features/backend/events/basic_sequence_event.feature b/features/backend/events/basic_sequence_event.feature
index 10808acc7..158b7472b 100644
--- a/features/backend/events/basic_sequence_event.feature
+++ b/features/backend/events/basic_sequence_event.feature
@@ -4,7 +4,7 @@ Feature: Events Resources
     @1: TEST FOR GET EVENTS /----------------------------------------------------------------------
     Scenario: List all the events (result 0 events)
         Given that I have a valid access_token
-        And I request "project/251815090529619a99a2bf4013294414/events"
+        And I request "project/74621721252eab0a6383731089824705/events"
         Then the response status code should be 200
         And the response charset is "UTF-8"
         And the response has 0 record
@@ -20,23 +20,22 @@ Feature: Events Resources
                 "evn_status": "ACTIVE",
                 "evn_action": "SEND_MESSAGE",
                 "evn_related_to": "SINGLE",
-                "tas_uid": "97192372152a5c78f04a794095806311",
-                "evn_tas_uid_from": "97192372152a5c78f04a794095806311",
+                "tas_uid": "46337349752eab0df6e7b61093784394",
                 "evn_tas_estimated_duration": 1,
                 "evn_time_unit": "DAYS",
                 "evn_when": 1,
                 "evn_when_occurs": "AFTER_TIME",
-                "tri_uid": "75916963152cc6ab085a704081670580"
+                "tri_uid": "95002116552eab0b786a743075022999"
             }
             """
-        And I request "project/251815090529619a99a2bf4013294414/event"
+        And I request "project/74621721252eab0a6383731089824705/event"
         Then the response status code should be 201
         And store "evn_uid" in session array
 
     @3: TEST FOR GET EVENTS /----------------------------------------------------------------------
     Scenario: List all the events (result 1 event)
         Given that I have a valid access_token
-        And I request "project/251815090529619a99a2bf4013294414/events"
+        And I request "project/74621721252eab0a6383731089824705/events"
         Then the response status code should be 200
         And the response charset is "UTF-8"
         And the response has 1 record
@@ -50,18 +49,18 @@ Feature: Events Resources
                 "evn_description": "change description",
                 "evn_status": "ACTIVE",
                 "evn_action": "SEND_MESSAGE",
-                "evn_related_to": "SINGLE",
-                "tas_uid": "97192372152a5c78f04a794095806311",
-                "evn_tas_uid_from": "97192372152a5c78f04a794095806311",
+                "evn_related_to": "MULTIPLE",
+                "evn_tas_uid_from": "46337349752eab0df6e7b61093784394",
+                "evn_tas_uid_to": "86505074952eab0e1007790039372925",
                 "evn_tas_estimated_duration": 1,
                 "evn_time_unit": "DAYS",
                 "evn_when": 1,
                 "evn_when_occurs": "AFTER_TIME",
-                "tri_uid": "75916963152cc6ab085a704081670580"
+                "tri_uid": "95002116552eab0b786a743075022999"
             }
             """
         And that I want to update a resource with the key "evn_uid" stored in session array
-        And I request "project/251815090529619a99a2bf4013294414/event"
+        And I request "project/74621721252eab0a6383731089824705/event"
         Then the response status code should be 200
         And the response charset is "UTF-8"
         And the type is "object"
@@ -71,7 +70,7 @@ Feature: Events Resources
     Scenario: Get a event (with change in "evn_description")
         Given that I have a valid access_token
         And that I want to get a resource with the key "evn_uid" stored in session array
-        And I request "project/251815090529619a99a2bf4013294414/event"
+        And I request "project/74621721252eab0a6383731089824705/event"
         Then the response status code should be 200
         And the response charset is "UTF-8"
         And the type is "object"
@@ -82,7 +81,7 @@ Feature: Events Resources
     Scenario: Delete a event
         Given that I have a valid access_token
         And that I want to delete a resource with the key "evn_uid" stored in session array
-        And I request "project/251815090529619a99a2bf4013294414/event"
+        And I request "project/74621721252eab0a6383731089824705/event"
         Then the response status code should be 200
         And the response charset is "UTF-8"
         And the type is "object"
@@ -90,7 +89,7 @@ Feature: Events Resources
     @7: TEST FOR GET EVENTS /----------------------------------------------------------------------
     Scenario: List all the events (result 0 events)
         Given that I have a valid access_token
-        And I request "project/251815090529619a99a2bf4013294414/events"
+        And I request "project/74621721252eab0a6383731089824705/events"
         Then the response status code should be 200
         And the response charset is "UTF-8"
         And the response has 0 record
\ No newline at end of file
diff --git a/workflow/engine/src/BusinessModel/Event.php b/workflow/engine/src/BusinessModel/Event.php
index df9ecd5ba..d5bdd4991 100644
--- a/workflow/engine/src/BusinessModel/Event.php
+++ b/workflow/engine/src/BusinessModel/Event.php
@@ -93,14 +93,28 @@ class Event
         if ( ($sProcessUID == '') || (count($dataEvent) == 0) ) {
             return false;
         }
-
-        $oProcess = new \Process();
-        if (!($oProcess->processExists($sProcessUID))) {
-            throw (new \Exception( 'This process doesn\'t exist!' ));
-        }
-
         $dataEvent = array_change_key_case($dataEvent, CASE_UPPER);
 
+        $this->validateProcess($sProcessUID);
+
+        if ($dataEvent['EVN_RELATED_TO'] == 'SINGLE') {
+            if (empty($dataEvent['TAS_UID'])) {
+                throw (new \Exception('The field "tas_uid" is required!'));
+            }
+            $this->validateTask($dataEvent['TAS_UID']);
+        } else {
+            if (empty($dataEvent['EVN_TAS_UID_FROM'])) {
+                throw (new \Exception('The field "evn_tas_uid_from" is required!'));
+            }
+            $this->validateTask($dataEvent['EVN_TAS_UID_FROM']);
+
+            if (empty($dataEvent['EVN_TAS_UID_TO'])) {
+                throw (new \Exception('The field "evn_tas_uid_to" is required!'));
+            }
+            $this->validateTask($dataEvent['EVN_TAS_UID_TO']);
+        }
+
+        $this->validateTrigger($dataEvent['TRI_UID']);
         if ( $create && (isset($dataEvent['ENV_UID'])) ) {
             unset($dataEvent['ENV_UID']);
         }
@@ -139,5 +153,47 @@ class Event
             throw $e;
         }
     }
+
+    public function validateProcess($proUid) {
+        $proUid = trim($proUid);
+        if ($proUid == '') {
+            throw (new \Exception('This process doesn\'t exist!'));
+        }
+
+        $oProcess = new \Process();
+        if (!($oProcess->processExists($proUid))) {
+            throw (new \Exception('This process doesn\'t exist!'));
+        }
+
+        return $proUid;
+    }
+
+    public function validateTask($taskUid) {
+        $taskUid = trim($taskUid);
+        if ($taskUid == '') {
+            throw (new \Exception('This task doesn\'t exist!'));
+        }
+
+        $oTask = new \Task();
+        if (!($oTask->taskExists($taskUid))) {
+            throw (new \Exception('This task doesn\'t exist!'));
+        }
+
+        return $taskUid;
+    }
+
+    public function validateTrigger($triUid) {
+        $triUid = trim($triUid);
+        if ($triUid == '') {
+            throw (new \Exception('This trigger doesn\'t exist!'));
+        }
+
+        $oTriggers = new \Triggers();
+        if (!($oTriggers->TriggerExists($triUid))) {
+            throw (new \Exception('This trigger doesn\'t exist!'));
+        }
+
+        return $triUid;
+    }
 }
 
diff --git a/workflow/engine/src/Services/Api/ProcessMaker/Project/Event.php b/workflow/engine/src/Services/Api/ProcessMaker/Project/Event.php
index b1c72cdcd..48bbb674d 100644
--- a/workflow/engine/src/Services/Api/ProcessMaker/Project/Event.php
+++ b/workflow/engine/src/Services/Api/ProcessMaker/Project/Event.php
@@ -85,13 +85,13 @@ class Event extends Api
      * @param string $evn_status {@from body} {@choice ACTIVE,INACTIVE}
      * @param string $evn_action {@from body} {@choice SEND_MESSAGE,EXECUTE_CONDITIONAL_TRIGGER,EXECUTE_TRIGGER}
      * @param string $evn_related_to {@from body} {@choice SINGLE,MULTIPLE}
-     * @param string $tas_uid {@from body} {@min 1}
-     * @param string $evn_tas_uid_from {@from body} {@min 1}
      * @param string $evn_tas_estimated_duration {@from body} {@min 1}
      * @param string $evn_time_unit {@from body} {@choice DAYS,HOURS}
      * @param string $evn_when {@from body} {@type float}
      * @param string $evn_when_occurs {@from body} {@choice AFTER_TIME,TASK_STARTED}
      * @param string $tri_uid {@from body} {@min 1}
+     * @param string $tas_uid {@from body}
+     * @param string $evn_tas_uid_from {@from body}
      * @param string $evn_tas_uid_to {@from body}
      * @param string $evn_conditions {@from body}
      *
@@ -111,13 +111,13 @@ class Event extends Api
         $evn_status,
         $evn_action,
         $evn_related_to,
-        $tas_uid,
-        $evn_tas_uid_from,
         $evn_tas_estimated_duration,
         $evn_time_unit,
         $evn_when,
         $evn_when_occurs,
         $tri_uid,
+        $tas_uid = '',
+        $evn_tas_uid_from = '',
         $evn_tas_uid_to = '',
         $evn_conditions = ''
     ) {
@@ -146,13 +146,13 @@ class Event extends Api
      * @param string $evn_status {@from body} {@choice ACTIVE,INACTIVE}
      * @param string $evn_action {@from body} {@choice SEND_MESSAGE,EXECUTE_CONDITIONAL_TRIGGER,EXECUTE_TRIGGER}
      * @param string $evn_related_to {@from body} {@choice SINGLE,MULTIPLE}
-     * @param string $tas_uid {@from body} {@min 1}
-     * @param string $evn_tas_uid_from {@from body} {@min 1}
      * @param string $evn_tas_estimated_duration {@from body} {@min 1}
      * @param string $evn_time_unit {@from body} {@choice DAYS,HOURS}
      * @param string $evn_when {@from body} {@type float}
      * @param string $evn_when_occurs {@from body} {@choice AFTER_TIME,TASK_STARTED}
      * @param string $tri_uid {@from body} {@min 1}
+     * @param string $tas_uid {@from body}
+     * @param string $evn_tas_uid_from {@from body}
      * @param string $evn_tas_uid_to {@from body}
      * @param string $evn_conditions {@from body}
      *
@@ -172,13 +172,13 @@ class Event extends Api
         $evn_status,
         $evn_action,
         $evn_related_to,
-        $tas_uid,
-        $evn_tas_uid_from,
         $evn_tas_estimated_duration,
         $evn_time_unit,
         $evn_when,
         $evn_when_occurs,
         $tri_uid,
+        $tas_uid = '',
+        $evn_tas_uid_from = '',
         $evn_tas_uid_to = '',
         $evn_conditions = ''
     ) {