@sabya3112 , the US-India tax treaty only allows a J-1 researcher to exclude certain US based income for up to two years and therefore be taxed as a US person. Note that since you are not an exempt person, you will be ( thereafter) taxed as a Resident for Tax purposes. The treaty does not have any retroactive clause ( in fact none of the treaties that I am aware of nor the model treaty docs ) and therefore there is no claw back of presumed taxes for the years that were excluded. Therefore I do not understand your concern -- please add more details as to why you think there is a claw back due .
Namaste ji
pk
