When a company document is uploaded with an expiry date the system will send an alert 1 day and 7 days before that expiry date to your company HR Mailbox remind them that it is due to expire.
These notifications are automated and cannot be turned off or changed.
You can set an expiry against a company document by going to
Documents > Company Documents > Upload
You will see the option for "expiry date" as per below. If you would like the above reminders, please be sure to enter an expiry date