Any fringe benefit that is not specifically exempt from Social Security taxes counts as wages. The amount of wages is the difference between the discount price you pay for the benefit and its fair market value.
Effective January 1, 1985, the following five categories of fringe benefits do not count as wages:
The minimum fringe (a property or service furnished by your employer that is so small in value that counting it would be impractical);
Gyms and other athletic facilities (the value of an employer-provided on-premises athletic facility);
No additional cost service (any service provided to you by your employer for your use);
Qualified employee discount (employee discount with respect to property or services); and
Working condition fringe (any service or property provided by your employer, such as a parking space).