To Do is a simple tool where all the activities [assigned]({{docs_base_url}}/user/manual/en/using-erpnext/assignments.html) to you and assigned by you are listed. You can also add your own to-do items in the list.
When task is completed, you should simply remove assignment from the assigned document. With this, task will be removed from your Todo list as well. For Todo which are not assigned via document, you can set their status as Closed from the Todo master itself.
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