If you haven't been in the US for more than 4 years, you don't need to pay these taxes. I was in a similar situation last year. Talk to your payroll people, they should be able to refund it (mine did).  If they don't, there is a way to get it refunded from the government as well. I'm sure if you google it, you will find a way. Getting it done through payroll is much easier and hassle free though.