This year I have a somewhat tricky situation for state income tax filing (US). I am a professor at a university in Colorado, but I'm spending the academic year in Connecticut on sabbatical leave, working on research projects here. I continue to receive a salary from my university in CO. I have moved out of my (rented) residence in CO, but will return there in mid-2020. I was required to get a driver's license and auto registration in CT.
My current understanding is that I must file 2019 income tax returns in both states, as a resident in CO and as a non-resident in CT, and that my salary during my sabbatical will be considered CT-source income, since I am "performing services" in CT. I am trying to figure out what resources can help me confirm whether this is correct. I have read the basic websites from both states (CO, CT) but I am still unsure about the definitions of certain terms, or how they apply in my case: "domicile", "legal residence", "business conducted", and so. I also don't know whether there may be important exceptions not mentioned there.
So my questions are:
Are there other authoritative sources of information that can help me resolve these questions?
Is there a way to get an "official" ruling on these questions from the two states before filing my taxes, or do I just have to take my best guess (possibly with professional advice) and hope that it holds up if I am audited?
I usually prepare my taxes by myself (without software), but is this something that really requires professional advice? If so, at what level? Consumer tax software, storefront tax prep firms, professional accountant, tax attorney, ...?
If so, can I expect to find a single advisor who can help me with both state returns, or should I consult a different advisor in each state?
Is there any special evidence or documentation regarding residency that I should collect in case I am audited by either state?
Please note that I am not asking anyone here to tell me whether my current understanding is right, or how I should file. With all due respect, you're not my accountant. Again, I'm looking for pointers to resources that will help me educate myself. (Also, that way an answer will be useful to more people than just me.)