A Flexible Spending Account (also called an FSA) is a separate employee benefit plan that allows you to save money for qualified health care expenses. Under this program, you direct a part of your pay into a special, tax-free account that you can use throughout the year to reimburse yourself for certain eligible out-of-pocket health care expenses.
Money accumulated in your FSA must be used within a specific period. If you don't use those tax-free dollars within that period you will lose them for good. Once a new period begins only the money accumulated in that new period will be accessible for spending.