Consequences of incorrect assessment of residency status for previous tax years?
I entered the US in 1993 on an L-1 visa and became a resident alien (greencard holder) in 1996. In 2003 I left the US and established residence in my home country, Germany. I continued to have income from US sources and therefore filed annual US federal tax returns using form 1040. My green card expired in 2006.
Currently I'm in the process of preparing my 2006 return using form 1040NR. I now realize that I probably should have used form 1040NR for the 2003 to 2005 tax years as well, because my US residency effectively ended with the date of my departure and not as previously thought with the expiration of my green card. If this is indeed correct, do I have to amend the 2003 to 2005 filings? Are there other consequences I need to be aware of?
Thank you very much in advance!