If you have completed a task, it's best to mark it complete, keeping the item on the Tasks list rather than deleting it. On the other hand, if you add a task by mistake or if you no longer need to complete a task, you might choose to delete it from the list.
TIP
Undoing the Deletion
You are not prompted to confirm the deletion, so be sure that you do want the task deleted. If you delete a task by accident and you immediately realize your mistake, you can undo the deletion by opening the Edit menu and choosing Undo . If you have performed other actions since the deletion, however, issuing the Undo command won't work; you'll have to re-create the task.