Do all employees have to participate?

This depends on plan design. Some employers may choose to make participation in this pre-tax benefit mandatory. Others may make it voluntary. Another variation is to make participation automatic unless the employee opts out in writing.

What if an employee elects to participate and later changes his or her mind?

Employee elections must be made prior to their eligibility effective date or at the beginning of any plan year. Employee elections are binding for the plan year unless the employee has a qualifying or life event (i.e. marriage, divorce, birth, etc.) or a significant increase in cost or modification of coverage under an insurance benefit.