Illinois Paycheck Calculator

Illinois has taxed income at a flat rate since the tax was introduced, because the state constitution requires it: income tax must be levied at a single, non-graduated rate. Changing that requires a constitutional amendment.

Voters were asked to do exactly that in November 2020, in a referendum that would have permitted graduated rates rising for higher earners. It was rejected. As a result Illinois remains a flat-tax state, and the rate has sat at 4.95% since 2017, when it rose from 3.75%.

For a paycheck, the practical effect is predictability. A raise does not push you into a higher state bracket, and your state marginal rate is identical to your state effective rate once exemptions are accounted for. It also means Illinois takes a proportionally larger bite from lower earners than a graduated system would, which is the core of the ongoing political argument about it.

Illinois starts from your federal adjusted gross income, then applies its own additions and subtractions. Two subtractions matter most for take-home pay.

First, Illinois allows a personal exemption allowance for each taxpayer and dependent. It is modest, and it phases out entirely above an income threshold, so higher earners get nothing from it.

Second — and much more significant — Illinois does not tax retirement income. Distributions from qualified plans, IRAs, most pensions and Social Security are all subtracted from Illinois taxable income. This is one of the most generous retirement exclusions in the country and a major reason retirees stay in the state despite its property taxes.

For working-age employees, a traditional 401(k) contribution reduces your federal taxable wages, and because Illinois builds on the federal figure, it reduces your Illinois tax too. That is a real difference from Pennsylvania, where the state ignores 401(k) deferrals. Increasing your contribution rate in Illinois saves you both federal and state tax.

Illinois has no municipal or county income tax. Chicago, despite its size and its budget pressures, does not levy a wage tax — repeated proposals for a city income tax or a commuter tax have not become law. Whether you work in the Loop, in Springfield or in a suburb, your income tax withholding is the same.

The trade-off shows up in property tax. Illinois consistently ranks in the top two or three states for effective property tax rates, and in parts of Cook County and the collar counties the annual bill on an ordinary family home runs well into five figures. Sales tax is also high once Chicago's local add-ons are included.

If you are comparing Illinois with a neighbouring state, this is the calculation that matters: Illinois often looks competitive on the payslip and much less so once housing is included. Indiana and Missouri, both nearby, have lower property taxes but local income taxes of their own, so the comparison is rarely a clean win either way.