I am F-1 student. I ted 140 and 485 concurrently in March 2005. I-140 was approved in April 2005.I went back China with AP in April 2006. After that my status became AOS.I got my green card in March 2007. In this board, some people said that AOS can not use 1040NR to file tax reurn. Because I have a stock account, I can not use 1040EZ. In order to avoid any possible trouble,I filed tax return for the year of 2006 through Liberty Tax Service. They still use 1040NR for my tax return. They said although I got my green card in 2007, I was still a non-resident status in 2006. My question is: Can I use F-1 $5000 treaty while I was in AOS status? Can I use 1040NR for 2006 tax return? What is right way to file 2006 tax return in my situation. Appreciate any input!