If approved, lawmakers could replace the state's flat-rate income tax with a graduated-rate structure.
So instead of everyone paying the current 4.95%, people with higher incomes would pay a higher income tax rate.
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But there is wide disagreement about the impact such a change could have on taxpayers, businesses and the state's finances.
ABC 7 Chicago spoke this week with Quentin Fulks, chairman and executive director of Vote Yes for Fairness, a group supporting the amendment, and Lissa Druss, a spokeswoman with the Coalition to Stop the Proposed Tax Hike Amendment.