You will need to file in the state of Illinois since that is your state of residence.
You must file a DC tax return if:
- You were a resident of the District of Columbia and you were required to file a federal tax return.
- Your permanent residence was in the District of Columbia for either part of or the full taxable year.
- You lived in the District of Columbia for 183 days or more during the taxable year, even if your permanent residence was outside the District of Columbia.
- You were a member of the armed forces and your home of record was the District of Columbia for either part of or the full taxable year.
- You are the spouse of an exempt military person or of any other exempt person such as a nonresident presidential appointee or an elected official.
For more information, see:
https://otr.cfo.dc.gov/page/individual-income-tax-filing-faqs
