I have noticed that there is a tax treaty between US and my country Bulgaria from 2007. I was non resident alien for tax purposes in 2007 and 2008 and still.
I want to claim the benefits of the treaty for the years of 2007 and 2008. And I have already submitted the federal and state tax forms for these calendar years claiming no tax treaty benefits. How can I claim tax treaty benefits for previous years.
Thank you.

When did you enter and depart the U.S. Your visa? Are you filing 2009 tax return?

I entered 2006 under F1 and I am still in US under F1 visa. I filed the 2009 tax return claiming treaty benefits.

On F-1 for 5 years you are nonresident and must file nonresident tax return and Form 8843.
You can file amended tax returns Form 1040X for 2007 and 2008.

Thank you very much.