Sometimes tasks are large enough that they need to be split into subtasks. Subtasks are identical to tasks in many respects. However, the largest difference between the two is that instead of having a project as the parent object, Subtasks have a task as the parent object. Subtasks can additionally be split up into further subtasks, but you should remember that too many levels of subtasks can create confusion.
When using subtasks, you cannot directly update the completion status of the parent task. As you update the status of the subtasks, the status of the parent task is updated automatically. Also, when you create subtasks, you can use dependencies only within peer subtasks. You cannot make a subtask dependant on a task that is directly associated with a project or with other subtasks that are associated with different tasks.
When you create subtasks, the screens and fields that you see are identical to screens and fields for creating parent tasks.
After you have created subtasks, you can view them. When you view a subtask, the Contextual Menu displays an additional choice, View Parent Task. When you click this menu item, @task takes you to the task details screen of the parent task.
Editing, moving, and deleting subtasks is identical to parent tasks. To do these, open the subtask, then in the Contextual Menu, click Edit Task, Delete Task, or Move Task.
You can also attach issues, documents, and notes to subtasks as you would to a task. SeeAbout Using Notes an d Attachments