Typically, when you are receiving active duty pay in the military, your state of residence is your HOR and that is where your income is taxed. Therefore, your entire military income should be taxed in CT and not in MA. See more information below from the state websites.
Per the Connecticut Department of Revenue:
You will be considered a full year resident of CT if you meet the conditions below:
Personnel whose home of record is Connecticut
- If your home of record is Connecticut you are a resident of Connecticut. As a resident you must file a resident return and pay any tax due unless you meet all of the following conditions for the entire taxable year:
You did not maintain a permanent place of abode in Connecticut;
You maintained a permanent place of abode outside Connecticut; and
You spent 30 days or less in Connecticut.
If you meet all three conditions, you are considered a nonresident of Connecticut for the taxable year. You do not have to file a Connecticut income tax return unless you had Connecticut tax withheld or you had any income from Connecticut sources. (NOTE: Military personnel who do not meet all of the conditions above but who lived outside the United States for an extended period of time may qualify to be treated as nonresidents under the "Group B Exception". See IP 2015(24) for the Group B Exception rules.)
Here is information from the Massachusetts Department of Revenue - non-resident military personnel are not considered residents of MA because:
Nonresident military personnel who have not established a legal residence in Massachusetts and who are stationed in Massachusetts may meet the 183 days test but will usually not meet the permanent place of abode test since army barracks are not considered a permanent place of abode. You may however, have to report Massachusetts source income earned other than from military sources.
