Flexible spending accounts help you stretch your dollars by letting you put pretax income into an account that you can dip into for health-related expenses that fall outside of your insurance coverage. The catch is that the funds in that account are available on a use-it-or-lose-it basis after you deposit them, and most of us lose it, leaving behind an average of $100 in these accounts. Depending on where you work, you might have until March 15 of next year to draw down that money, or you could have only until the end of the calendar year.