Illinois Capital Gains Tax, Explained
A flat 4.95% on every gain — and a retirement-income exemption that means WHICH account you sell from decides whether Springfield gets paid. We'd know; we're headquartered there.
A guide by Taxstra Tax & Accounting — CPA-led tax strategy for business owners
Quick Answer
Illinois taxes capital gains as ordinary income at a flat 4.95% — no long-term discount — on top of the federal 0/15/20% brackets and 3.8% NIIT. The twist that matters: Illinois doesn't tax retirement income at all, so gains inside a 401(k)/IRA come out Illinois-tax-free while identical gains in a brokerage account pay 4.95%. Enter 4.95 in the state field of our capital gains tax calculator for your combined number.
The Flat 4.95%: Simple Math, Federal Strategy
Illinois keeps it brutally simple: gain × 4.95%, whether you held for a week or a generation. No brackets to fill, no cliffs to dodge, no state-level discount to chase. That pushes all the interesting strategy federal — hold past one year, harvest in low-income years, use the 0% federal bracket — and Illinois automatically inherits every dollar you shave off federal AGI.
| Sale | Illinois (4.95%) | Typical federal add-on | Combined |
|---|---|---|---|
| $100,000 LTCG, $175K household | $4,950 | ~$15,000 (15%) | ~$19,950 (≈20%) |
| $400,000 LTCG, $350K household | $19,800 | ~$75,200 (15% + NIIT) | ~$95,000 (≈24%) |
| $100,000 short-term gain, top bracket | $4,950 | ~$37,000 + NIIT | ~$45,750 (≈46%) |
The Retirement Exemption: Illinois's Great Asymmetry
Illinois is one of the friendliest states in America to retirement-account money and completely indifferent to your brokerage account. Distributions from 401(k)s, IRAs, and pensions — including every dollar of gain earned inside them — leave the state untaxed. The same $50,000 of appreciation realized in a taxable account pays $2,475 to Springfield.
For Illinois retirees, that turns two ordinary decisions into real money: withdrawal sequencing (drawing from the IRA versus selling in the brokerage account changes the state bill directly) and Roth conversions, which generally escape Illinois tax on the way out of the traditional account. The federal side still runs the show — bracket-fill math, IRMAA, the works — but Illinois quietly subsidizes the retirement-account route.
Asset location is worth more in Illinois
If future gains will be realized anyway, holding the growth assets inside retirement accounts and the stable assets in taxable — the classic asset-location play — carries an extra 4.95% payoff here. It's a portfolio-design decision with a tax return attached.
Homes, Rentals, and the Payment Step Everyone Misses
Because Illinois starts from federal AGI, the Section 121 exclusion ($250K/$500K on a primary residence), installment-sale treatment, and 1031 exchange deferral all flow through automatically — the 1031 exchange rules defer the 4.95% right alongside the federal bill. Rental sellers should model federal depreciation recapture (up to 25%) plus Illinois's flat rate, and anyone leaving a home behind should weigh selling versus renting it out while the exclusion window is open.
Illinois expects its money in the quarter you sell
Both the IRS and Illinois run pay-as-you-go systems. A large gain means an estimated payment that quarter — or a year-end withholding rescue. The safe-harbor math is in our estimated tax payments guide, and the penalty check takes a minute.
Estimated tax payments guide · Penalty calculator
One more note, since this is our home turf: Taxstra is headquartered in Springfield, Illinois and serves clients in all fifty states — Illinois returns, multi-state situations, and everything the flat 4.95% touches are daily work here.
Illinois Capital Gains FAQs
Selling in Illinois — or planning the drawdown?
We model the flat 4.95%, the retirement-account asymmetry, the federal stack, and the payment plan as one picture. Illinois-based, serving all fifty states.
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