Income Tax Rates

Illinois currently has a flat income tax rate of 3.75%, meaning the percentage does not go up as your income rises. Missouri, meanwhile, starts off at 5% and increases with your income. Kentucky also starts off at 5% and is progressive. Wisconsin, also progressive, starts off at 4%. Indiana, with a flat 3.23% is the only state bordering Illinois with a lower flat income tax rate than Illinois has. Iowa has a lower starting tax rate at only .36% but has the highest state income tax for its top earners at 8.98%