Your filing status for Connecticut income tax purposes must be the same as your filing status for federal income tax purposes with the following exceptions:

If one spouse is a resident and the other is a nonresident, each spouse who is required to file a Connecticut income tax return must file as married filing separately for Connecticut income tax purposes even if they file a joint federal income tax return unless they both consent to be treated as residents.
If one spouse is a resident or a nonresident and the other spouse is a part-year resident, they must file as married filing separately for Connecticut income tax purposes even if they file a joint federal return.
If one spouse is a nonresident with Connecticut source income and the other is a nonresident with no Connecticut source income, the spouse with Connecticut source income must file as married filing separately even if they file a joint federal return unless they both consent to be treated as if they have Connecticut source income. For example, if you are a resident of Rhode Island who works in Connecticut, but your spouse is a resident of Rhode Island who has no Connecticut source income, you should file a separate Form CT-1040NR/PY even if you and your spouse file a joint federal income tax return. or
If both spouses are part-year residents and moved into or out of Connecticut at different times during the taxable year, both spouses must file as "married, filing separate." However, if both spouses are part-year residents and moved into or out of Connecticut on the same day and filed jointly for federal income tax purposes, a joint Connecticut income tax return, Form CT-1040NR/PY, must be filed.
NOTE: Recent legislation allows same sex partners to enter into a civil union in Connecticut on or after October 1, 2005. However, civil union partners are not permitted to file a joint Connecticut income tax return for 2005. Civil union partners must file their 2006 Connecticut income tax returns using one of the following filing statuses: civil union filing jointly or civil union filing separately