When you finish your portion, or the whole of, a task, you click 'I'm Done' on My Assignments screen (see illustration here).
This causes the task to disappear from My Assignments.
However, if you have been working on the task along with other assignees, and they still unfinished with their work on the task, it will not get the completed status until the last of the assignees clicks 'I'm Done'.



'Work is done' check mark
To indicate who of the assignees have completed their portion of a task, each assignee has the 'Work is done' check mark available in Activity details screen.
Completing task
The task will close when the last of its assignees clicks the 'I'm Done' button.

Users X and Y are working on the same task called 'Design Website'.
Since the task is active, they both will have it on their In Progress tab, My Assignments.
As user X finishes his part, he clicks 'I'm Done'. This will have a three-fold effects:
- The task disappears from user X's My Assignments page.
- In Design Website task's details, in Assignees section, user X will have the 'work is done' checkbox selected automatically.
- The task's status will not change.
User Y will, as before, have the task on his My Assignments page, and the task will not get Completed status until user Y clicks 'I'm Done'.