Social security and medicare are mandatory taxes withheld for US citizens and resident (only few classes of non resident alien are exempt from Social security and medicare tax). They are always a fixed percentage of your gross income. So there is nothing to worry about those. You don't ignore those taxes but fill them in the 1040 (w-2 part) for informational purpose only. However, federal tax withheld is the part of money that is withheld from your paycheck every time. And depending on the math (how much was withheld and how much you owe IRS and some other credits like education credit, health care credit, 401k, etc.), you will either have to pay or get the refund.