Notifications can be automatically sent to internal users(and employees on active assignments). To set this up you would need to have Notification Management enabled in your Admin menu. If it is not enabled, go to Admin-->User Management, look at your preferences and enable it there.
You can manage the credential notification via the Notification Management screen(Admin-->Notification Management):
You have the ability to send emails, texts messages, and Akken popups for any expiring credentials for candidates and/or employees.