IRS rules require you to forfeit any balance left in your FSAs at the end of the plan year — the “use it or lose it” rule. You must incur eligible expenses by December 31st, and submit them for reimbursement before April 1, 2016. However, there will be a grace period, so you can use remaining funds to pay for the next calendar year expenses incurred through March 15 just by swiping your card.

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