State tax filing

File a resident Massachusetts return and a non-resident Connecticut return. You can claim a credit on your MA return for tax paid to CT.

All your income is taxable to MA because you are residents. Any income earned while working in CT is taxed by Connecticut. If your wife works in CT once a week, then approximately 20% of that income is CT income (1 of 5 days).

CT allows you to file either jointly or separately. If you file together, your tax rate will be based on your total income, but you’ll only pay tax on the CT percentage.

For example, if you earned $100,000 everywhere, then your CT base income would be $100,000. If the CT tax on $100,000 is $x and you earned $50,000 in CT then your part-year/non-resident tax would be 50% ($50k/$100k) of $x.

It may be more beneficial to file married filing separately in CT.

See How do I prepare a joint federal return and separate state returns?