I want to see completed tasks, how do I do that?
Unfortunately, it's not possible to view the completed tasks list on the iPhone app right now, but we will consider adding such option in future updates.
You're welcome to vote for this request in our Votebox: http://todoist.com/Vote_iOS/showProposal/7/
It also requires a Premium account to access your completed tasks. Please check out that feature and many more of our Premium service! https://todoist.com/pricing