Thanks for your quick response,I really appreciated. According to our suggestion,I don't get all the Federal Withholding.. If I file form 1040 NR.. If I use INDIA-US TREATY ARTICLE 22... I can get all the refund... Can I do like that?. Sorry to trouble you.. I am just confusing... please provide me the answers..

Suresh:

Article 22 applies to teachers, researchers and visiting acholars.

If you are on OPT, you are NONE of the above. Article 21 applies to you, and it states that only income from OUTSIDE the United States is exempt from U.S. taxes. You pay on OPT is from a U.S. source earned while INSIDE the United States, so it is fully taxable.