Hi. I was a resident of California for a while, paid CA taxes, have CA driver license, car is registered in CA, etc. The nature of my job requires travelling. Last June, I got a project in Illinois. Since June, I'm renting apartment here in IL. It is a long project so I might stay here for a few more months, but I don't plan to live here after project ends. I also don't plan to return to California. Actually, I'm planning to settle in New Hampshire. I still pay CA taxes which doesn't make sense to me. My question is whether it is possible to establish New Hampshire residency before I end my project here in IL, so I can save on state income tax? I won't be able to make permanent move to New Hampshire before I end my project in IL, does it mandates me to pay either CA or IL state income tax during this period? Thanks.

“ I also don't plan to return to California. Actually, I'm planning to settle in New Hampshire. I still pay CA taxes which doesn't make sense to me. “----->UNLESS you move into IL or NH as a part year resident of IL or NH, you are a still full year resident of CA and need to pay CA tax on your CA source income and income that you earn in IL .
“My question is whether it is possible to establish New Hampshire residency before I end my project here in IL, so I can save on state income tax?”-------> I guess this is not tax related question.I don’t think so UNLESSS you are physically present in NH. When you end yur project in IL and move into NH then you need to file your CA tax as a part year resident and you also need to file youir NH return as a part year resident too. In this case, you do not need to report your CA source income to NH and vice versa. However, you still need to re[ort your IL source income to IL and CA as a full year resident of CA and a nonresident of IL.
“I won't be able to make permanent move to New Hampshire before I end my project in IL, “-------> I guess so until you are physically present in NH. You need to be physically present in NH to be a full year resident of NH.
“does it mandates me to pay either CA or IL state income tax during this period?”------>Now you are still full year resident of CA even if you are working in IL as a nonresident of IL; since there is no State Tax Reciprocal Agreements between IL and CA, you need to pay tax on your income that you earn in IL to IL and as a full year resident of CA, you can claim your IL tax on your CA return. As long as CA tax rate is higher than that in IL, you can fully deduct your IL tax paid to IL on your CA return.

Thank you!
What if I temporary go to NH, rent apartment( I won't be able to live here full time ), change driver license and car registration to NH, open bank account here and then return to IL to finish my project here. Will it be sufficient to change my tax residency to NH?

“What if I temporary go to NH, rent apartment( I won't be able to live here full time ), change driver license and car registration to NH, open bank account here and then return to IL to finish my project here. Will it be sufficient to change my tax residency to NH?”-----> Establishing residency in a new state, NH in this case, can be performed generally in the same manner in all of the 50 US states. However, you need to check any specific NH state and the particular part of the state that interests you for more details. This would include the length of time you must live in that NH state in order to qualify legally as a state resident. Be sure to examine NH state’s specifications for making actual residency complete. Some US states require you live in the location for only six months. Other states require a full year to establish residency. You will need to get an in-state drivers license / an actual street address in your new state, and not a P.O. box or a Private Mail Box address, which is often listed as only a street address. The US Postal Service can determine fraudulent residencies in this way and this can cost you at least a hefty fine. You may not establish residency in two different US states, because this could lead to multiple voting in federal elections and this is a crime. You might own homes in two or more states, but you can only choose one US State as your primary residence.
So, as long as you live in IL as your home state as a full year resident of IL, you can simultaneously never be a full year resident of NH.