If you will not have a permanent residence when you move to Germany I would recommend using a friend or relatives address in one of the state tax exempt states (ie. Florida, Texas, Washington, etc) This way you will only have to file a federal tax return. I lived in Germany for 9 years as a military brat, and 2 years in Okinawa in the service. This was good advice that was given to me. Take every opportunity to enjoy Germany it is a wonderful country and has events happening every weekend in many towns.