You would have to check with the plan administrator. For example, if you set up a maximum $5000 FSA, and only submitted reimbursements for $4900, then you have $100 in the account that is forfeit (you can't get it back). If you set up and FSA and billed for the full amount then you don't have any forfeit amount. If you don't know what you did, try to get a statement from the plan administrator.
