Tasks marked as completed will move from In Progress Tasks on your Tasks page, to the Completed Tasks section.
They will remain here to be viewed at any given time. By clicking the expand icon you are able to view the details of the task. If it is decided that the task has not been successfully completed, click on the Uncomplete button located at both the top and bottom of the page.
The task will then return to the In progress Tasks section.
At this point if the task is overdue it will be highlighted in red and indicate 'Task Overdue'.