Indiana Code Title 6. Taxation § 6-3-5-3

Sec. 3.  The department of state revenue, with the approval of the governor and the budget agency after the review of the state budget committee, may enter into an agreement with the state of Illinois that establishes a methodology for determining individual income taxes paid by residents of each state to the other state and an obligation, in exchange for a like obligation on the part of Illinois, to make a payment to Illinois.  The payment obligation by Indiana may not be greater than the difference between the amount of Indiana individual adjusted gross income taxes for the previous taxable year that would be collected from: