Illinois Paycheck Tax Calculator (2026 Flat 4.95%)

Illinois is one of the simplest state income taxes to compute and one of the more interesting ones to plan around. The tax itself is a flat 4.95% on Illinois taxable income, with no brackets, no local income taxes, and a bonus withholding rate identical to the regular rate. The calculator above applies that math directly.

The planning questions come from geography and income mix. Illinois sits in a cluster of reciprocity states, hosts a large commuter workforce from Wisconsin, Indiana, Iowa, and beyond, and its flat rate interacts differently with high incomes than a graduated state would. Notably, Illinois also exempts retirement income entirely, which changes the retirement-location math.

For high earners, flat means flat: there is no millionaire bracket, so a $1 million Illinois wage earner pays the same 4.95% marginal rate as a $60,000 earner. That makes Illinois cheaper at the top than its headline reputation suggests, though property taxes tell a different story.

Illinois applies 4.95% to Illinois base income after subtracting the personal exemption allowance. There are no rate brackets to manage and no bracket creep. The rate has been 4.95% since July 2017, and no 2026 legislation changed it. A 2020 ballot measure to allow graduated rates failed, so a constitutional flat-rate guarantee remains in place.

Two Illinois-specific subtractions matter for planning. Retirement income (Social Security, pensions, 401(k) and IRA distributions) is fully exempt, one of the most generous treatments in the country. And Illinois does not tax nonresidents on retirement income regardless of where it was earned, per federal law.

Worth saying plainly for Chicago workers: there is no city income tax. Unlike New York City, Philadelphia, or the Ohio cities, Chicago levies no wage tax of its own, so the 4.95% state rate really is the entire income-tax line on a Chicago paycheck. The city collects its share through property and sales taxes instead, which is where the Illinois stack gets expensive.

Illinois has wage reciprocity agreements with Iowa, Kentucky, Michigan, and Wisconsin. A resident of any of those states who earns W-2 wages in Illinois can file Form IL-W-5-NR with the employer to stop Illinois withholding and pay only the home state. The agreement runs in reverse too: an Illinois resident working in those four states pays only Illinois.

Indiana is the notable gap. Despite the long shared border and the Chicago-to-Northwest-Indiana commute pattern, Illinois and Indiana have no reciprocity agreement, so those commuters file nonresident returns and use the resident credit instead. Missouri, the other significant commuter border in the Metro East, is the same story: two returns and a credit, every year.

As everywhere, reciprocity covers W-2 wages only. A Wisconsin-based locum physician taking 1099 shifts in Illinois still files an Illinois nonresident return and claims a Wisconsin credit.

Illinois employees file Form IL-W-4 to claim exemption allowances. Because the tax is flat, withholding accuracy is mostly automatic: bonuses and RSU vesting are withheld at the same flat 4.95% that applies to all other income, so the common high-earner problem of supplemental withholding overshooting or undershooting the real rate largely disappears at the state level.

The underwithholding risk in Illinois is therefore concentrated in non-wage income: 1099 side income, pass-through business profit, and investment gains have no withholding at all and require estimated payments once liability is meaningful. The federal side, with its graduated brackets, remains the usual source of paycheck surprises.

An Illinois resident is taxed on all income everywhere, with a credit for income tax properly paid to other states on the same income. The credit is capped at the Illinois tax on that income. Because 4.95% is a comparatively low rate, Illinois residents working in higher-rate states (New York, California, Minnesota) usually find the credit fully absorbed, meaning they net-pay the other state’s higher rate.

The reverse is favorable: an Illinois resident earning income in a lower-rate or no-tax state pays Illinois only the difference or the full 4.95% respectively. For traveling professionals, the practical work is keeping a defensible day-and-dollar allocation by state so both the nonresident returns and the Illinois credit line up.

Two quick contrasts show the range. An Illinois consultant earns $50,000 on a California engagement: California taxes it at graduated rates that exceed 4.95% at her income level, the Illinois credit caps at $2,475 (4.95% of $50,000), and the California excess is unrecoverable. The same consultant earns $50,000 on a Texas engagement: Texas charges nothing, no credit exists or is needed, and Illinois simply collects its $2,475. Identical fees, identical days away from home, materially different after-tax outcomes, which is why engagement pricing for multi-state professionals should quote states, not just rates.

A W-2 employee living and working in Illinois has one of the simplest state situations in the country: flat rate, matching bonus withholding, no local income tax. The genuine planning cases are cross-border commuters (especially Indiana, where no reciprocity exists), multi-state 1099 earners, retirees weighing the full exemption of retirement income against high property taxes, and business owners deciding where pass-through income is sourced.

Retirement deserves emphasis: because Illinois exempts retirement income entirely, a high-property-tax state becomes surprisingly competitive for retirees who rent or downsize. The income-tax line of a relocation spreadsheet should be near zero for an Illinois retiree, which changes the usual Sun Belt comparison.

Four groups get a return on a projection that a flat-rate calculator cannot deliver. Cross-border households where one spouse works in Indiana or Missouri, states with no Illinois reciprocity, so the couple runs credits and split withholding every year. Physicians and consultants stacking multi-state 1099 income on Illinois wages, who need per-state estimates and an allocation log. Owners of pass-through businesses with out-of-state revenue, where apportionment decides how much profit is Illinois-taxable and where the state’s pass-through entity tax election can change the federal deduction picture. And pre-retirees timing the shift from taxable wages to fully exempt retirement income, where a one-year acceleration or deferral of income moves real dollars.

A realistic scenario: a Chicago hospitalist with a $320,000 W-2 adds $90,000 of 1099 locum work split between Wisconsin and Iowa. Both are reciprocity states, but reciprocity covers only wages, so the 1099 income is taxed by Wisconsin and Iowa on nonresident returns, credited against Illinois up to 4.95%. She needs two nonresident filings, two estimate schedules, an Illinois credit computation, and a check on whether her employer’s Illinois withholding leaves room for the credit math to land. That is a projection, not a paycheck problem.