diff --git a/cvat/apps/dataset_manager/tests/test_formats.py b/cvat/apps/dataset_manager/tests/test_formats.py
index 1eb3e2b5..54f5d286 100644
--- a/cvat/apps/dataset_manager/tests/test_formats.py
+++ b/cvat/apps/dataset_manager/tests/test_formats.py
@@ -218,8 +218,6 @@ class TaskExportTest(_DbTestBase):
     def _generate_task(self, images):
         task = {
             "name": "my task #1",
-            "owner": '',
-            "assignee": '',
             "overlap": 0,
             "segment_size": 100,
             "labels": [
@@ -435,8 +433,6 @@ class FrameMatchingTest(_DbTestBase):
     def _generate_task(self, images):
         task = {
             "name": "my task #1",
-            "owner": '',
-            "assignee": '',
             "overlap": 0,
             "segment_size": 100,
             "labels": [
diff --git a/cvat/apps/engine/serializers.py b/cvat/apps/engine/serializers.py
index 2fe598f5..a6b8dee7 100644
--- a/cvat/apps/engine/serializers.py
+++ b/cvat/apps/engine/serializers.py
@@ -83,8 +83,8 @@ class JobSerializer(serializers.ModelSerializer):
     task_id = serializers.ReadOnlyField(source="segment.task.id")
     start_frame = serializers.ReadOnlyField(source="segment.start_frame")
     stop_frame = serializers.ReadOnlyField(source="segment.stop_frame")
-    assignee = BasicUserSerializer(allow_null=True)
-    assignee_id = serializers.IntegerField(write_only=True, allow_null=True)
+    assignee = BasicUserSerializer(allow_null=True, required=False)
+    assignee_id = serializers.IntegerField(write_only=True, allow_null=True, required=False)
 
     class Meta:
         model = models.Job
@@ -274,10 +274,10 @@ class TaskSerializer(WriteOnceMixin, serializers.ModelSerializer):
     size = serializers.ReadOnlyField(source='data.size')
     image_quality = serializers.ReadOnlyField(source='data.image_quality')
     data = serializers.ReadOnlyField(source='data.id')
-    owner = BasicUserSerializer()
-    owner_id = serializers.IntegerField(write_only=True, allow_null=True)
-    assignee = BasicUserSerializer(allow_null=True)
-    assignee_id = serializers.IntegerField(write_only=True, allow_null=True)
+    owner = BasicUserSerializer(required=False)
+    owner_id = serializers.IntegerField(write_only=True, allow_null=True, required=False)
+    assignee = BasicUserSerializer(allow_null=True, required=False)
+    assignee_id = serializers.IntegerField(write_only=True, allow_null=True, required=False)
 
     class Meta:
         model = models.Task
@@ -285,7 +285,7 @@ class TaskSerializer(WriteOnceMixin, serializers.ModelSerializer):
             'bug_tracker', 'created_date', 'updated_date', 'overlap',
             'segment_size', 'status', 'labels', 'segments',
             'project', 'data_chunk_size', 'data_compressed_chunk_type', 'data_original_chunk_type', 'size', 'image_quality', 'data')
-        read_only_fields = ('mode', 'created_date', 'updated_date', 'status', 'data_chunk_size',
+        read_only_fields = ('mode', 'created_date', 'updated_date', 'status', 'data_chunk_size', 'owner', 'asignee',
             'data_compressed_chunk_type', 'data_original_chunk_type', 'size', 'image_quality', 'data')
         write_once_fields = ('overlap', 'segment_size')
         ordering = ['-id']
diff --git a/cvat/apps/engine/tests/test_rest_api.py b/cvat/apps/engine/tests/test_rest_api.py
index b7448fff..2b3d7378 100644
--- a/cvat/apps/engine/tests/test_rest_api.py
+++ b/cvat/apps/engine/tests/test_rest_api.py
@@ -297,47 +297,47 @@ class JobUpdateAPITestCase(APITestCase):
         self.assertEqual(response.data["id"], self.job.id)
         self.assertEqual(response.data["status"], data.get('status', self.job.status))
         assignee = self.job.assignee.id if self.job.assignee else None
-        self.assertEqual(response.data["assignee"], data.get('assignee', assignee))
+        self.assertEqual(response.data["assignee"]["id"], data.get('assignee_id', assignee))
         self.assertEqual(response.data["start_frame"], self.job.segment.start_frame)
         self.assertEqual(response.data["stop_frame"], self.job.segment.stop_frame)
 
     def test_api_v1_jobs_id_admin(self):
-        data = {"status": StatusChoice.COMPLETED, "assignee": self.owner.id}
+        data = {"status": StatusChoice.COMPLETED, "assignee_id": self.owner.id}
         response = self._run_api_v1_jobs_id(self.job.id, self.admin, data)
         self._check_request(response, data)
         response = self._run_api_v1_jobs_id(self.job.id + 10, self.admin, data)
         self.assertEqual(response.status_code, status.HTTP_404_NOT_FOUND)
 
     def test_api_v1_jobs_id_owner(self):
-        data = {"status": StatusChoice.VALIDATION, "assignee": self.annotator.id}
+        data = {"status": StatusChoice.VALIDATION, "assignee_id": self.annotator.id}
         response = self._run_api_v1_jobs_id(self.job.id, self.owner, data)
         self._check_request(response, data)
         response = self._run_api_v1_jobs_id(self.job.id + 10, self.owner, data)
         self.assertEqual(response.status_code, status.HTTP_404_NOT_FOUND)
 
     def test_api_v1_jobs_id_annotator(self):
-        data = {"status": StatusChoice.ANNOTATION, "assignee": self.user.id}
+        data = {"status": StatusChoice.ANNOTATION, "assignee_id": self.user.id}
         response = self._run_api_v1_jobs_id(self.job.id, self.annotator, data)
         self._check_request(response, data)
         response = self._run_api_v1_jobs_id(self.job.id + 10, self.annotator, data)
         self.assertEqual(response.status_code, status.HTTP_404_NOT_FOUND)
 
     def test_api_v1_jobs_id_observer(self):
-        data = {"status": StatusChoice.ANNOTATION, "assignee": self.admin.id}
+        data = {"status": StatusChoice.ANNOTATION, "assignee_id": self.admin.id}
         response = self._run_api_v1_jobs_id(self.job.id, self.observer, data)
         self.assertEqual(response.status_code, status.HTTP_403_FORBIDDEN)
         response = self._run_api_v1_jobs_id(self.job.id + 10, self.observer, data)
         self.assertEqual(response.status_code, status.HTTP_404_NOT_FOUND)
 
     def test_api_v1_jobs_id_user(self):
-        data = {"status": StatusChoice.ANNOTATION, "assignee": self.user.id}
+        data = {"status": StatusChoice.ANNOTATION, "assignee_id": self.user.id}
         response = self._run_api_v1_jobs_id(self.job.id, self.user, data)
         self.assertEqual(response.status_code, status.HTTP_403_FORBIDDEN)
         response = self._run_api_v1_jobs_id(self.job.id + 10, self.user, data)
         self.assertEqual(response.status_code, status.HTTP_404_NOT_FOUND)
 
     def test_api_v1_jobs_id_no_auth(self):
-        data = {"status": StatusChoice.ANNOTATION, "assignee": self.user.id}
+        data = {"status": StatusChoice.ANNOTATION, "assignee_id": self.user.id}
         response = self._run_api_v1_jobs_id(self.job.id, None, data)
         self.assertEqual(response.status_code, status.HTTP_401_UNAUTHORIZED)
         response = self._run_api_v1_jobs_id(self.job.id + 10, None, data)
@@ -356,7 +356,7 @@ class JobPartialUpdateAPITestCase(JobUpdateAPITestCase):
         self._check_request(response, data)
 
     def test_api_v1_jobs_id_admin_partial(self):
-        data = {"assignee": self.user.id}
+        data = {"assignee_id": self.user.id}
         response = self._run_api_v1_jobs_id(self.job.id, self.owner, data)
         self._check_request(response, data)
 
@@ -1073,9 +1073,11 @@ class TaskGetAPITestCase(APITestCase):
         self.assertEqual(response.data["size"], db_task.data.size)
         self.assertEqual(response.data["mode"], db_task.mode)
         owner = db_task.owner.id if db_task.owner else None
-        self.assertEqual(response.data["owner"], owner)
+        response_owner = response.data["owner"]["id"] if response.data["owner"] else None
+        self.assertEqual(response_owner, owner)
         assignee = db_task.assignee.id if db_task.assignee else None
-        self.assertEqual(response.data["assignee"], assignee)
+        response_assignee = response.data["assignee"]["id"] if response.data["assignee"] else None
+        self.assertEqual(response_assignee, assignee)
         self.assertEqual(response.data["overlap"], db_task.overlap)
         self.assertEqual(response.data["segment_size"], db_task.segment_size)
         self.assertEqual(response.data["image_quality"], db_task.data.image_quality)
@@ -1179,11 +1181,13 @@ class TaskUpdateAPITestCase(APITestCase):
         mode = data.get("mode", db_task.mode)
         self.assertEqual(response.data["mode"], mode)
         owner = db_task.owner.id if db_task.owner else None
-        owner = data.get("owner", owner)
-        self.assertEqual(response.data["owner"], owner)
+        owner = data.get("owner_id", owner)
+        response_owner = response.data["owner"]["id"] if response.data["owner"] else None
+        self.assertEqual(response_owner, owner)
         assignee = db_task.assignee.id if db_task.assignee else None
-        assignee = data.get("assignee", assignee)
-        self.assertEqual(response.data["assignee"], assignee)
+        assignee = data.get("assignee_id", assignee)
+        response_assignee = response.data["assignee"]["id"] if response.data["assignee"] else None
+        self.assertEqual(response_assignee, assignee)
         self.assertEqual(response.data["overlap"], db_task.overlap)
         self.assertEqual(response.data["segment_size"], db_task.segment_size)
         image_quality = data.get("image_quality", db_task.data.image_quality)
@@ -1213,7 +1217,7 @@ class TaskUpdateAPITestCase(APITestCase):
     def test_api_v1_tasks_id_admin(self):
         data = {
             "name": "new name for the task",
-            "owner": self.owner.id,
+            "owner_id": self.owner.id,
             "labels": [{
                 "name": "non-vehicle",
                 "attributes": [{
@@ -1229,7 +1233,7 @@ class TaskUpdateAPITestCase(APITestCase):
     def test_api_v1_tasks_id_user(self):
         data = {
             "name": "new name for the task",
-            "owner": self.assignee.id,
+            "owner_id": self.assignee.id,
             "labels": [{
                 "name": "car",
                 "attributes": [{
@@ -1277,7 +1281,7 @@ class TaskPartialUpdateAPITestCase(TaskUpdateAPITestCase):
 
         data = {
             "name": "new name for the task",
-            "owner": self.owner.id
+            "owner_id": self.owner.id
         }
         self._check_api_v1_tasks_id(self.admin, data)
         # Now owner is updated, but self.db_tasks are obsolete
@@ -1300,8 +1304,8 @@ class TaskPartialUpdateAPITestCase(TaskUpdateAPITestCase):
         self._check_api_v1_tasks_id(self.user, data)
 
         data = {
-            "owner": self.observer.id,
-            "assignee": self.annotator.id
+            "owner_id": self.observer.id,
+            "assignee_id": self.annotator.id
         }
         self._check_api_v1_tasks_id(self.user, data)
 
@@ -1339,8 +1343,9 @@ class TaskCreateAPITestCase(APITestCase):
         self.assertEqual(response.status_code, status.HTTP_201_CREATED)
         self.assertEqual(response.data["name"], data["name"])
         self.assertEqual(response.data["mode"], "")
-        self.assertEqual(response.data["owner"], data.get("owner", user.id))
-        self.assertEqual(response.data["assignee"], data.get("assignee"))
+        self.assertEqual(response.data["owner"]["id"], data.get("owner_id", user.id))
+        assignee = response.data["assignee"]["id"] if response.data["assignee"] else None
+        self.assertEqual(assignee, data.get("assignee_id", None))
         self.assertEqual(response.data["bug_tracker"], data.get("bug_tracker", ""))
         self.assertEqual(response.data["overlap"], data.get("overlap", None))
         self.assertEqual(response.data["segment_size"], data.get("segment_size", 0))
@@ -1377,7 +1382,7 @@ class TaskCreateAPITestCase(APITestCase):
     def test_api_v1_tasks_user(self):
         data = {
             "name": "new name for the task",
-            "owner": self.assignee.id,
+            "owner_id": self.assignee.id,
             "labels": [{
                 "name": "car",
                 "attributes": [{
@@ -1653,8 +1658,8 @@ class TaskDataAPITestCase(APITestCase):
         response = self._get_task(user, task_id)
 
         expected_status_code = status.HTTP_200_OK
-        if user == self.user and "owner" in spec and spec["owner"] != user.id and \
-           "assignee" in spec and spec["assignee"] != user.id:
+        if user == self.user and "owner_id" in spec and spec["owner_id"] != user.id and \
+           "assignee_id" in spec and spec["assignee_id"] != user.id:
             expected_status_code = status.HTTP_403_FORBIDDEN
         self.assertEqual(response.status_code, expected_status_code)
 
@@ -1736,8 +1741,8 @@ class TaskDataAPITestCase(APITestCase):
     def _test_api_v1_tasks_id_data(self, user):
         task_spec = {
             "name": "my task #1",
-            "owner": self.owner.id,
-            "assignee": self.assignee.id,
+            "owner_id": self.owner.id,
+            "assignee_id": self.assignee.id,
             "overlap": 0,
             "segment_size": 100,
             "labels": [
@@ -2034,8 +2039,8 @@ class TaskDataAPITestCase(APITestCase):
     def test_api_v1_tasks_id_data_no_auth(self):
         data = {
             "name": "my task #3",
-            "owner": self.owner.id,
-            "assignee": self.assignee.id,
+            "owner_id": self.owner.id,
+            "assignee_id": self.assignee.id,
             "overlap": 0,
             "segment_size": 100,
             "labels": [
@@ -2080,8 +2085,8 @@ class JobAnnotationAPITestCase(APITestCase):
     def _create_task(self, owner, assignee):
         data = {
             "name": "my task #1",
-            "owner": owner.id,
-            "assignee": assignee.id,
+            "owner_id": owner.id,
+            "assignee_id": assignee.id,
             "overlap": 0,
             "segment_size": 100,
             "labels": [