I am a student in the United States. I have graduated in May 2011 and I am working in the United States. Now I am on my OPT. My question is that I am subject to all kind of taxes? I was exempt fom Medcare and social Security tax but lately they started deducting that from my account as well. I don't know what has changed with the new year. I am not sure if there is a new law passed that now Students working on their OPT, OPTIONAL PRACTICAL TRAINING should pay tax?

WHEN did you first arrive in U.S.

If you arrived in the U.S. in 2007, then 2011 was your FIFTH year in the U.S. so you became liable for FICA (Social Security and Medicare) taxes on 1 January 2012.