State residence

It depends on your residency status and where you earned your income.

Explanation:

• Since your home address and voting place are in Indiana, you are considered an Indiana resident. You should file as a full-year resident of Indiana and report all income (including Illinois) as required by Indiana.
• llinois Non-Resident Filing: As an Indiana resident who earned income in Illinois, you need to file an Illinois non-resident tax return (Form IL-1040 and Schedule NR) to report the income earned in Illinois
• Indiana Tax Credit: You can claim a credit on your Indiana state tax return (Form IT-40) for the taxes paid to Illinois. This prevents double taxation on the same income.
• Reciprocity Agreement: Indiana and Illinois do not have a reciprocity agreement. This means you must file tax returns in both states.

For more information, you can refer to the Illinois Department of Revenue and the Indiana Department of Revenue.

Q. Do I use Indiana or Illinois to file state taxes ? 

A. Both, per the details at the other reply.