Just_78-Mob:
I think you mean how do you claim a refund for Social Security and Medicare taxes withheld by mistake?
The form is Form 843. The procedures and additional documentation is spelled out in IRS Pub 519 (I believe page 45).
However, before you file this form, you need to ask your employer to refund the withheld Social Security and Medicare taxes. If they refuse, you need to get them to write a memo saying why they cannot refund the withheld Social Security and Medicare taxes and how much should have been refunded to you. If they refuse to write the memo, you need to produce a statement saying the same thing.
You will also need to provide a copy of your visa, plus other documentation that shows you were in country on an OPT. It's all in the IRS Pub 519.
You can contact me at
[email protected] if you have detailed questions that you do not want to reveal on this forum.