Comman man, don't you understand English. The letter only refers to social security taxes not federal and state income taxes. Go and look into your W2, there are seperate sections for SS tax, medicare,federal, state tax etc. All these taxes are different taxes. There is no reason to panic. If you do not pay SS taxes then you dont qualify for certain benefits. If you are not permanent resident or citizen of this country you do not qualify for SS benefits even if you pay SS taxes (there are some exemptions) so why pay for somethign if you will not be claiming it in the future. Most schools payroll offices dont deduct these taxes for F1 students.