Illinois taxes the poorest 20 percent of its residents at a higher level than the national average; it’s one of the few states above 13 percent, 2.7 percent above the national average.
It’s above average for the middle class, as well: the national average for the middle 60 percent is 9.4 percent, so Illinois is 1.7 percent above the national average. Only Arkansas (11.2 percent), Hawaii (11.3 percent), and New York (11.2 percent) tax the middle class at higher rates than Illinois.
As you go up the tax bracket, the effective state and local tax rate falls, but it remains relatively high. Illinois taxes the top 80-95 percent of residents at nine percent, behind only Arkansas and Connecticut (just barely), Wisconsin (9.7 percent), and New York (11 percent), and 1.3 percent above the national average. The 95-99 percent income bracket gets hit at 7.6 percent, just a bit above the national average of 7.2 percent.
Only on the top one percent does Illinois fall below the national average: 4.9 percent compared to 5.6 percent.