check the link here: it's official IRS link - [url=http://www.irs.gov/Individuals/International-Taxpayers/Foreign-Student-Liability-for-Social-Security-and-Medicare-Taxes]http://www.irs.gov/Individuals/International-Taxpayers/Foreign-Student-Liability-for-Social-Security-and-Medicare-Taxes[/url] The highlight is this sentence: The exemption does not apply to F-1,J-1,M-1, or Q-1/Q-2 nonimmigrants who become resident aliens. So your HR and payroll people were correct about F1 doesn't have to pay SS tax, however, that only applies when you are Non resident alien F1.