如果你是持學生簽證且在美國居住五年內的non-resident alien，你的工作所得不需要扣繳交社會安全(Social security tax) 及醫療稅 (Medicare Tax)。
原文請見Chapter 8, Publication 519：
If you are a nonresident alien temporarily admitted to the United States as a student, you generally are not permitted to work for a wage or salary or to engage in business while you are in the United States. In some cases, a student admitted to the United States in “F-1,” “M-1,” or “J-1” status is granted permission to work. Social security and Medicare taxes are not withheld from pay for the work unless the student is considered a resident alien.
請注意，如果你持學生簽證在美國超過五年，則在稅法上必須視為resident alien，需要繳交Social security and Medicare taxes。其實這兩種稅是美國的社會福利制度，當你需要繳這兩種稅的時候，代表你可以享有美國的社會福利。從另外一個角度想，或許不是件壞事～
13.5 Aliens and U.S. Citizens Living Abroad: Nonresident Alien - Tax Withholding
Under my visa as a temporary nonresident alien, I'm not subject to social security and Medicare withholding. My employer withheld the taxes from my pay. What should I do to get a refund of my social security and Medicare?
If social security tax and Medicare were withheld in error from pay received that was not subject to the taxes, you must first contact the employer who withheld the taxes for reimbursement. If you are unable to get a refund from the employer, file a claim for refund with the Internal Revenue Service on Form 843 (PDF), Claim for Refund and Request for Abatement.
You must attach the following to your claim:
* a copy of your Form W-2 (PDF), Wage and Tax Statement, to prove the amount of tax withheld;
* Form I-797, INS Approval Notice, is needed if you have changed your status from F-1 or J-1 to another status prior to filing the claim;
* if your visa status changed during the tax year you should attach copies of the pay stubs that cover the period of exemption from social security taxes;
* a copy of INS Form I-94, Arrival/Departure Record, if you are still in the United States;
* a copy of your valid entry visa;
* Form 8316, Information Regarding Request for Refund of Social Security Tax, or a signed statement stating that you have requested a refund from the employer and have not been able to obtain one; and
* a copy of Form 1040NR (PDF), US Nonresident Alien Income Tax Return (or Form 1040NR-EZ (PDF)), for tax the year in question. Processing of your claim may be delayed if you submit it less than six weeks after you filed Form 1040NR or 1040NR-EZ.
In addition to the documentation listed above foreign student visa holders should also attach the following:
* a copy of Form I-20, Certificate of Eligibility, endorsed by your student advisor and stamped by the Bureau of Citizenship and Immigration Services; and
* a copy of the Employment Authorization Document of your Optional Practical Training (e.g., Form I-766, I-538 or 688B).
* if you are an exchange visitor, attach a copy of Form IAP-66 or DS-2019 to your claim.
File the claim, with attachments, with the IRS where the employer's returns were filed. If you do not know where the employer's returns were filed, send your claim to the Internal Revenue Service Center, Philadelphia, PA 19255.
For more information, refer to Chapter 8 of Publication 519, U.S. Tax Guide for Aliens.
(From: Frequently Asked Tax Questions And Answers)