just so it's clear..... by "under retirement age" means you are under 59.5 years old, you are unlikely to avoid the 10% penalty for withdrawing. You also would owe the normal federal tax. For Ilinois, there is no penalty for the state tax, but you would pay normal Illinois income tax.
Why are you withdrawing? maybe you are eligible for a different exception to the 10% penalty?
https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-exceptions-to-tax-o...
