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Illinois Bonus Tax Calculator

Estimate take-home pay on a bonus, using the federal flat-rate supplemental withholding method

Estimate only — not tax advice. Federal tax on the bonus uses the flat 22% supplemental withholding rate (37% on cumulative supplemental wages over $1,000,000/year) — the alternative "aggregate method" some employers use instead is not modeled. FICA and any state SDI/PFL are computed as the difference between your regular income with and without the bonus added, so the Social Security wage cap applies correctly. State tax on the bonus is a marginal-bracket estimate, not necessarily any special state supplemental rate. See methodology below for source and last-verified date.

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How Illinois Paycheck Tax Is Calculated (2026)

Source: Illinois Department of Revenue
Flat state rate4.95%
Personal exemption$2,425
state_tax = max(0, gross_income - 2425) × 0.0495

Federal Tax & FICA (shared across all states)

Filing statusStandard deduction
Single$16,100
Married Filing Jointly$32,200
Head of Household$24,150
Federal brackets (all filing statuses)10% / 12% / 22% / 24% / 32% / 35% / 37%
Social Security6.2% up to $184,500 wage base
Medicare1.45% on all wages, +0.9% above $200,000 single/HoH, $250,000 MFJ

Guideline version 2026-IL-v1 · Last verified 2026-07-26

Illinois Paycheck Calculator FAQ

What is Illinois's state income tax rate?

Illinois charges a flat 4.95% income tax rate on all taxable income — the Illinois Constitution (art. IX, § 3) prohibits graduated rates. Each filer gets a $2,425 personal exemption in 2026.

Does Illinois tax retirement income?

No — Illinois does not tax Social Security, pension income, or 401(k)/IRA withdrawals, making it comparatively favorable for retirees despite the flat wage tax.

Does Illinois have local income tax?

No. Unlike Pennsylvania or Ohio, no Illinois city or county adds a separate local income tax on top of the state's flat 4.95% rate.

Methodology & Source

Illinois state tax figures sourced from Illinois Department of Revenue (https://tax.illinois.gov/), citing 35 ILCS 5/201 — flat 4.95% rate (Illinois Constitution art. IX, § 3 prohibits graduated rates). Federal brackets, standard deductions (single/MFJ/HoH), and FICA constants sourced from the IRS (Revenue Procedure 2025-32; married-filing-jointly Additional Medicare threshold of $250,000 is a separate, unindexed statutory figure). Illinois's married-filing-jointly and head-of-household figures have been independently verified against the source above.

Bonus federal withholding uses the flat supplemental-wage rate (22%, 37% above $1,000,000 cumulative supplemental wages/year), per IRS Publication 15 (Circular E), Employer's Tax Guide, 2026 edition — the alternative "aggregate method" is not modeled.

This is an estimate based on standard single-filer federal, FICA, and IL state calculations. Actual withholding may differ based on your W-4 elections, pre-tax deductions (401k, health insurance), and other factors.

Guideline version: 2026-IL-v1 · Effective: 2017-07-01 · Last verified: 2026-07-26