Your military pay is free of Connecticut income tax if you keep no permanent home in Connecticut, keep a permanent home outside Connecticut and spend 30 days or less in Connecticut during the year. Dormitory type housing does not count as a permanent home. If you do not meet all three conditions but lived outside the United States for an extended period, you may still be treated as a nonresident under the Group B Exception.
There is nothing to file in advance. File your Connecticut return as a nonresident and keep records showing where your permanent home was and how many days you spent in Connecticut. Check the Group B Exception rules first if you were living abroad.
Proof of a permanent residence outside Connecticut, your orders, and a record of the days you spent in Connecticut during the tax year.
