Final answer:
The main disadvantage of using a flexible spending account (FSA) for employees is the risk of losing money if funds are not used by the year-end deadline.
Step-by-step explanation:
The main disadvantage to an employee when using a flexible spending account (FSA) is Employees risk losing their money at the end of year if funds are not used by the year-end deadline. This is because unused funds in an FSA typically do not roll over to the next year and are forfeited. It's important for employees to carefully estimate their eligible expenses to avoid losing money.