Two of the most important concepts to understand about FSAs are the Grace Period and Run-Out Period. Money in a FSA account should be used by the end of December for the calendar year enrolled. For example, if you enroll in a FSA during annual enrollment of 2015, you should use your funds by December of 2016.
But, there is a Grace Period following the Flex Plan Year that lasts until March 15 of each year, which allows you to use the previous year’s flexible spending funds to pay for expenses incurred during the Grace Period. If you still haven’t used the money in your account by the end of the Grace Period, you’ll lose it.
The Run-Out Period lasts until April 30 for submitting claims. You have to have all your claims in by April 30, to be able to cover your expenses with your previous year’s money.