There are two relevant terms: domicile and resident. The general rule is that a person can have only one domicile but more than one residence. Each state has its own laws as to whether you are subject to their income taxes. Generally states have at least a presumption that if you are there a certain period of time, most frequently 180 days, or 183 days or 6 months, you are a resident for income tax purposes but you in fact may be taxed even sooner, when you become domiciled in a state, which may be as soon are move there and you intend to make that state your home.
A quick look at the internet (
which may or may not be correct) indicates that Indiana's rules (for income tax purposes) about residency and domicile are:
The term “resident” means (a) any individual who was domiciled in Indiana
during the taxable year; (b) any individual who maintains a permanent place
of residence in Indiana and spends more than one hundred eighty three (183)
days of the taxable year in Indiana; (c) any estate of a deceased person
defined in (a) or (b); or (d) any trust which has a situs in Indiana.
* * *
A person has only one domicile at a given time even though that person
maintains more than one residence at that time. Once a domicile has been
established, it remains until the conditions necessary for a change of
domicile occur.
In order to establish a new domicile, the person must be physically present at
a place, and must have the simultaneous intent of establishing a home at that
place. It is not necessary that a person intend to remain there until death;
however, if the person, at the time of moving to the new location, has
definite plans to leave that new location, then no new domicile has been
established.
http://www.in.gov/dor/reference/files/ib55.pdf
This is just an introduction to the issues you face. You will have to look at both Illinois and Indiana rules and look at part year residency rules for filing of tax returns as well. My
guess is that you will file tax returns in Illinois for the time you lived there and in Indiana once you move there, and any goofing around trying to maintain your domicile in Illinois after you have moved to Indiana to avoid taxes in Indiana may backfire. The last thing you want is to end up with liabilities in both states.
Just food for thought. As I emphasized, you need to look at all the rules carefully and I only pointed to some of the issues. See my signature line if you haven't already figured out that this is not legal advice.