After you have finished working on a task assigned to you, you can mark it as completed. You can mark a task completed either in the Task List page or in the Task Details page.
Normally, a task assigned to a group appears as an Available task in the task list of all team members. The actual team member to complete the task is marked as the performer.
While this is a transparent operation, this task may still appear on the Task List of other team members until they refresh their displays. Other team members attempting to complete the same task will receive a message informing them that the task has already been completed.
Team members who open their Task List after the original user has completed the task, cannot see the task in their Task List.