If you purchased a license for an employee who has left the company, you might be able to use that license for another employee.
Here's how you'll know when you can and cannot use a license for someone else.
If the assigned license has feedback responses, you cannot transfer the license to someone else. However, if the assigned license has no feedback associated with it, you can transfer it to someone else.
Deleting all assessments with no feedback responses returns the license to your account, allowing you to use it for someone else.
You can check how many licenses are in use at any time from your Billing page.