Hello, I am a research scholar working in the US on J1 visa I got up to one year. I will comes under tax treaty between India-US for research scholar on J1 visa. I want to know if my J1 status if it extended to another 2 years, I have to pay the taxes from the beging or from the date of extension.
Could you please help me with this reply. Thank you

Yes, if your stay exceeds 2 years, the exemption is lost for the entire visit. Read IRS Publication 901. Tax Treaties.

Here is the link to the treaty on the IRS website; you need to review Article 22:

http://www.irs.gov/pub/irs-trty/india.pdf