Tap the checkbox to complete a task.

Depending on your checkmark settings, the task may be automatically archived as well.

To explicitly archive a task you can long-tap the task and choose Archive from the popup menu.

If you are viewing archived tasks you can tap the checkmark to re-open the task.

To move a task to the Trash long-tap the task and choose Move to Trash.

If you make a mistake, tap the Undo button.