Normally, candidates' submissions are stored in Inspera for up to two years. After two years, the submissions may be permanently removed from the system.
The "Allow students to sign off own submission" setting allows candidates to permanently remove their submission from the system when they access it. This includes both submission and marking for that submission. The submission will be deleted from the view of the candidate as well as from the view of the planner and grader. In some countries this is a legal requirement. We do not recommend that you activate this feature unless there is a specific requirement for it in your institution.
Settings for Planner
The Planner can choose to enable the option for candidates to sign off their own submission in the After test settings when creating a test.
To access this setting, the Allow candidates post-submission review option must be enabled. This can be enabled at any time.
Candidate experience
The candidate sign in to the Inspera as usual, and can then find the test in the archive. Under "See more details", the candidate will be given the choice to remove their answer. 
You can read more about how candidates can sign off their submissions in the article Sign off submission - for candidates.