Hi,

I am a German J1 postdoc and worked here in the current position for half a year (since summer 2011). I am exempt from the federal tax because of the German-US tax treaty.
However, I have been working and living in the US before on a J1 VISA, but a different position (2004 to 2006). Am I still exempt from the taxes, or do I have them all to pay back.?

The treaty benefit is avaiable only once. So you can not claim benefits in 2011.