This field displays the date this line (task) was completed. It is set automatically when the actioner changes this task from status 'In progress' (or 'Pending') to 'Completed'.
If this task is reverted from status 'Completed' to status 'In progress' or 'Pending' the system will automatically delete the date.
You must be logged in as the assigned actioner to set a task status. The QA manager or Planner (project manager) for this non-conformance incident is not permitted to add status tracking information on your behalf.