Can I use funds from my current FSA plan to pay for an expense incurred during my previous FSA plan?
FSA funds in a plan year can only be used for expenses incurred during the plan year. For example, your 2018 FSA funds cannot cover an expense from 2017. However, there is a 90-day runout period at the end of the plan in which you can submit claims for reimbursement for expenses during that plan year.