See the following on the Maine Revenue Services web site.
I did not live in Maine for the entire year. Do I have to file a return?
If you have no Maine-source income you do not have to file a Maine tax return. Any interest or other investment income, pension income, etc. that you receive, or that is credited to your account, after you move to Maine is Maine-source income. And, of course, if you do work in Maine at all before the end or the year, any money that you earn is Maine-source income.
