diff --git a/backend/src/main/java/core/entities/timemanager/TaskSerieItem.java b/backend/src/main/java/core/entities/timemanager/TaskSerieItem.java
index 3160a78..533a931 100644
--- a/backend/src/main/java/core/entities/timemanager/TaskSerieItem.java
+++ b/backend/src/main/java/core/entities/timemanager/TaskSerieItem.java
@@ -1,6 +1,7 @@
 package core.entities.timemanager;
 
 import javax.persistence.*;
+import java.util.Objects;
 
 @Entity
 @Table(name = "task_series_items")
@@ -61,4 +62,17 @@ public class TaskSerieItem {
     public void setTask(Task task) {
         this.task = task;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        TaskSerieItem that = (TaskSerieItem) o;
+        return itemID == that.itemID;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(itemID);
+    }
 }
diff --git a/backend/src/main/java/core/services/TaskSeriesService.java b/backend/src/main/java/core/services/TaskSeriesService.java
index 8c5614b..5952dab 100644
--- a/backend/src/main/java/core/services/TaskSeriesService.java
+++ b/backend/src/main/java/core/services/TaskSeriesService.java
@@ -15,6 +15,7 @@ import org.springframework.stereotype.Service;
 
 import java.time.LocalDate;
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.List;
 
 @Service
@@ -65,6 +66,7 @@ public class TaskSeriesService {
     public void deleteTaskSeriesItem(Task task) {
         TaskSerieItem item = task.getTaskSerieItem();
         TaskSerie taskSerie = task.getTaskSerieItem().getTaskSerie();
+        taskSerie.getTasks().remove(item);
         task.setTaskSerieItem(null);
         taskSerieItemRepository.delete(item);
         if(taskSerie.getTasks().isEmpty()) {
@@ -73,9 +75,27 @@ public class TaskSeriesService {
             }
             taskSerie.getTasks().clear();
             taskSeriesRepository.delete(taskSerie);
+        } else {
+            repearIndexing(taskSerie);
         }
     }
 
+    private void repearIndexing(TaskSerie taskSerie) {
+        taskSerie.getTasks().sort(Comparator.comparingInt(TaskSerieItem::getSeriesIndex));
+        List<TaskSerieItem> updatedItems = new ArrayList<>();
+        int currentIndex = 1;
+        for(TaskSerieItem taskSerieItem : taskSerie.getTasks()) {
+            if(taskSerieItem.getSeriesIndex() != currentIndex) {
+                taskSerieItem.setSeriesIndex(currentIndex);
+                updatedItems.add(taskSerieItem);
+            }
+
+            currentIndex++;
+        }
+
+        taskSerieItemRepository.saveAll(updatedItems);
+    }
+
     public void deleteTaskSerieByTaskgroup(Taskgroup taskgroup) {
         taskSerieItemRepository.deleteByTaskgroup(taskgroup);
         taskSeriesRepository.deleteUnreferenced();