<prompt> Human: So Ive bought a house in CT may 2015, but I work across state lines in Mass.I thought I only need to file state tax in the state where I work, which is Mass for several reasons - friend advice and turbotax being not helpful.So for year 2015 and possibly year 2016 I still need to check later - I erroneously filed state taxes as Mass resident... This year so for tax year 2017 - I finally did file for both..Recently I got this audit letter from CT dept of revenue services: :-Our records show that you did not file a Connecticut Income tax return for tax year 2015. Based on information we received from the IRS under 6103d of the internal revenue code, we believe you may owe income tax to the State of Connecticut. You must do take the following action to settle this matter: 1 File your tax using the instrctions below; pay taxes 1037; interest fine 5400 2 Complete page 2 of this notice telling us why you were not required to file.I have the following questions: A Why the fuck did they audit me only now? What information made them finally audit me now? Is that standard practice to audit 3 years later? B Why only 2015 and not 2016 as well since I think I also didnt file CT return for 2016... Is that fine also coming? C does 6103d has any special significance? or is this a standard wording? D Why does CT wants so much? They estimate state tax for 2015 as 3400 based on 72k income from federal return apparently. Is it possible that they are coming from the wrong idea that I actually worked in CT and not in Mass? E On the back of the form it says that one of the reasons for why I didnt file CT return would be that I was a resident of another state and in this case I can provide a copy of my State return to prove it or a driver license copy. Since I technically filed as Mass resident for 2015 - can I just do that? what investigative powers do they have?  <response>: B Theyll eventually get around to 2016, since you now know its a problem, you can get to filing and paying to reduce the penalties and interest that are accumulating with each day. D The reason CT wants so much is because they assume you have no credits or deductions, plus theres about 3 years of interest and fines tacked on for failing to file. You should be able to get a credit for taxes paid to MA on your CT tax return. If MA has a higher tax rate than CT, youd likely owe CT very little or nothing. If CT has the higher tax rate, then youd owe the difference. In total across both states, you essentially always pay the higher tax rate of the state you live in vs. the state you work in. If you can get a tax credit for taxes paid to MA, the interest and penalties you owe should also be recalculated based on the new amount you owe. E Dont add tax fraud to your problems, you were at least a part year resident of CT in 2015. 