flat income tax Illinois Issues: Flat Vs. Graduated Income Tax By Mike Klemens and Ralph Martire • Aug 24, 2017 401ktaxcalculator.org Commentary: Should Illinois' current flat-tax system be changed as the state attempts to deal with its ongoing budget struggles? Illinois Representative Says He'll Push Graduated Income Tax Proposal By Sarah Mueller • May 3, 2016 ilga.gov The sponsor of a proposal to move Illinois to a graduated income tax says he is going forward with it Wednesday after working to shore up support. Time for a Change? Call Coming for Illinois' Leaders to Bring Voters a Choice to Alter Constitution By Jamey Dunn • Jan 1, 2014 WUIS/Illinois Issues When the framers of Illinois’ Constitution, which was adopted in 1970, were considering the revenue article, the state’s income tax was practically brand new.