Illinois Taxes on RSUs and Stock Options: A Tech Employee's Guide

Chicago has a deep and established technology sector — not the coastal giant of San Francisco or Seattle, but a significant ecosystem in its own right. CME Group, Motorola Solutions, Zebra Technologies, Paylocity, Morningstar, Tempus AI, and Sprout Social are among the publicly traded tech-adjacent companies headquartered in the Chicago metro with meaningful equity compensation programs. A substantial cluster of high-growth private companies — Relativity, project44, Enova, Avant, and numerous FinTech and InsurTech startups — rounds out an ecosystem where RSUs, ISOs, and NSOs are a standard part of senior-engineer compensation. And a growing share of Chicago-area tech workers are remote employees of FAANG and other coastal companies, receiving equity from grants issued while working elsewhere.

The Illinois tax structure for tech workers has several characteristics worth knowing before your next vest event. The headline: Illinois taxes all income — RSU vests, salary, bonuses, capital gains — at a flat 4.95% state rate.¹ There is no preferential rate for long-term capital gains. But Illinois also has no state alternative minimum tax on ISO exercises — a meaningful advantage compared to California's 7% state AMT and Colorado's 3.47% AMT.² Chicago levies no personal income tax of its own. The one notable tax trap: Illinois has a separate state estate tax with an $8 million exemption that is not portable between spouses — far below the federal $15 million exemption under OBBBA and a real planning issue for senior tech workers with meaningful accumulated wealth.

Illinois tax structure for tech employees at a glance

RSUs in Illinois

At vest: ordinary income taxed at 4.95%

When RSUs vest, the fair market value of the shares at the vesting date is ordinary income — taxed federally at your marginal rate (22–37% depending on total comp) and by Illinois at 4.95%. Your employer withholds at the IRS 22% supplemental rate federally plus Illinois 4.95% state withholding on supplemental wages. For senior engineers whose marginal federal rate is 32% or 37%, the 22% federal withholding creates a significant shortfall that must be addressed through estimated quarterly tax payments or a W-4 adjustment. The RSU after-tax calculator models the exact federal and state withholding gap for your income level.

Example: a senior engineer at Motorola Solutions in Schaumburg vests $180,000 of RSUs in 2026. Federal income tax at 35% marginal rate = $63,000. Illinois state tax at 4.95% = $8,910. Additional Medicare Tax (0.9%) on income above $200K = factored in at marginal level. Total tax on that vest: approximately $74,000+. After-tax proceeds: approximately $106,000. The 4.95% Illinois rate is meaningfully lower than California's 13.3% top rate — an Illinois engineer vesting the same RSU amount saves roughly $15,000 in state tax compared to their California counterpart.

After vest: capital gains taxed at 4.95%

Your cost basis in vested RSU shares is the FMV at vest. If you hold and later sell at a higher price, the gain is a capital gain. At the federal level, long-term capital gains (shares held 12+ months from vest) qualify for preferential 0/15/20% federal rates. Illinois does not conform — all capital gains, short-term and long-term alike, are taxed at the flat 4.95% rate.

The practical implication: there is no Illinois state tax incentive to hold RSU shares for more than 12 months. The federal incentive remains real — the difference between a 37% federal ordinary income rate and a 20% federal LTCG rate on $200,000 of appreciation is $34,000. But that saving is entirely from the federal side. Illinois is neutral on the hold-versus-sell decision post-vest.

ISOs and Illinois' no-AMT advantage

Illinois' most significant advantage for startup employees with incentive stock options is the absence of a state-level alternative minimum tax. ISO exercises do not trigger any Illinois AMT liability — the ISO bargain element does not create an Illinois-specific tax event separate from the regular income tax structure.

The state AMT comparison

Concretely: a startup engineer in Chicago exercises ISOs with a $600,000 bargain element in 2026. Federal AMT on that spread — after the $90,100 single-filer exemption and phaseout starting at $500,000 — is approximately $150,000+. California would add another $42,000 (7% state AMT on the full $600,000 element). Illinois adds nothing: the ISO exercise creates no separate Illinois AMT event. The regular Illinois income tax (4.95%) applies only when and if the employee later sells the shares in a disqualifying disposition.

This matters most for pre-IPO startup employees in Chicago's growing FinTech and HealthTech ecosystem — particularly those holding ISOs in companies approaching liquidity events. The ISO AMT calculator models federal AMT exposure and the maximum shares exercisable with zero AMT in a given year.

Qualifying vs. disqualifying dispositions in Illinois

• Qualifying disposition (hold ≥2 years from grant AND ≥1 year from exercise): the bargain element is a federal AMT preference item — no Illinois AMT equivalent. When sold, the gain is a long-term capital gain federally (0/15/20%), but taxed at 4.95% by Illinois (no LTCG preference). Illinois recognizes the income at sale, not at exercise.
• Disqualifying disposition (sell before meeting both holding periods): the spread at exercise becomes ordinary income federally and is taxed by Illinois at 4.95% in the year of sale. No separate Illinois AMT event. Any remaining appreciation above the spread is a short-term capital gain — also 4.95% in Illinois.

NSOs in Illinois

Non-qualified stock options are taxed at exercise: the spread (FMV at exercise minus strike price) is ordinary income, taxed by Illinois at 4.95%. There is no AMT event for NSOs at either the federal or Illinois state level. Post-exercise appreciation held for 12+ months is a long-term capital gain at the federal level — but taxed at 4.95% by Illinois (same as short-term). The decision whether to hold NSO shares after exercise is driven by concentration risk and federal tax considerations, not Illinois-specific factors.

ESPP in Illinois

§423 Employee Stock Purchase Plans follow the same federal income-recognition structure, with Illinois taxing all components at 4.95%:

• Disqualifying disposition: the ordinary income component (the discount, including any look-back benefit) is Illinois income at 4.95%; short-term gain above the spread is also 4.95%.
• Qualifying disposition: the smaller of (a) the discount at grant or (b) the gain over the original offering-period starting price is ordinary income at 4.95% in Illinois; any remaining appreciation above that is a long-term capital gain — also 4.95% in Illinois.

Since Illinois gives no LTCG preference, the qualifying vs. disqualifying distinction is driven almost entirely by federal tax considerations. See the ESPP guide and ESPP calculator for after-tax modeling.

The Illinois estate tax: the gap you need to know about

Illinois is one of a handful of states that maintains a separate state estate tax independent of the federal system. This is the tax area where Illinois creates meaningful complexity for high-earning tech employees that other no-estate-tax states (Virginia, Washington, Texas, Florida) do not.

The $8 million exemption — and why it's not enough

Effective January 1, 2026, the Illinois estate tax exemption increased from $4 million to $8 million.³ Estates below $8 million owe no Illinois estate tax. Estates above $8 million are subject to Illinois estate tax at graduated rates up to 16%. The federal estate tax exemption under OBBBA is $15 million per person — nearly double Illinois' threshold.

For a senior engineer who has accumulated significant equity wealth, this gap matters. Consider a staff engineer with: $2.5M in a brokerage account (vested RSUs appreciated over a decade), $1.2M in 401(k)/IRA, $1.5M home, $600K in unvested RSUs, and $2M in company stock. Net estate: approximately $7.8M — close to but under the $8M threshold, with unvested equity and market appreciation potentially pushing it over. That same individual owes nothing to the federal estate tax (well below $15M) but may have a real Illinois estate tax exposure as their equity program continues to deliver.

The portability problem

The federal estate tax exemption is portable between spouses: if the first spouse to die doesn't fully use their $15M exemption, the surviving spouse can elect to carry over the unused portion, effectively giving a married couple a $30M combined exemption. Illinois does not allow portability. Each spouse has a $8M Illinois exemption — use it or lose it.³

The practical consequence: a married couple where one spouse dies with a $10M estate can fully shelter it from federal estate tax via portability. But if their estate was concentrated in the deceased spouse's name (common when one partner carries most of the equity comp), Illinois takes its cut on the $2M above the $8M threshold before the surviving spouse inherits. A bypass trust (AB trust) or QTIP trust that intentionally funds a credit shelter trust at first death can preserve both spouses' $8M Illinois exemptions — but this requires intentional advance planning, not just a simple "I love you will."

Moving from California to Illinois: what changes for equity

The California-to-Chicago move is less common than California-to-Texas or California-to-Florida, but it does happen — particularly for finance-adjacent tech roles in Chicago's FinTech ecosystem, and for engineers whose companies allow fully remote work from anywhere. The state income tax savings are real (13.3% → 4.95%), though Illinois' estate tax means it's not a clean slate on all fronts.

California long-arm sourcing still applies to old grants

California taxes RSU income based on the proportion of the grant-to-vest period spent working in California — regardless of where you live when the shares vest.⁶ If you spent 2 of 4 years in California on a particular grant before moving to Illinois, California claims 50% of each vest event on that grant as California-source income. Illinois simultaneously claims the Illinois-apportioned portion based on your working days in Illinois. This can create partial double-state-tax exposure on the same income — partially offset by credits — until all pre-move grants have finished vesting.

The California equity tax guide and the remote work state tax guide cover the sourcing mechanics and credit interaction in detail.

Annual income tax comparison after the move

For a senior engineer with $300K in annual RSU vests, moving from California to Illinois reduces state income tax by approximately $25,000 per year — significant, though less than a move to Texas or Florida where state income tax is zero. The ISO AMT comparison is more dramatic: a California employee exercising $500K in ISO bargain element pays $35,000 in state AMT that an Illinois employee doesn't owe at all.

Illinois state tax reciprocity agreements

Illinois has reciprocity agreements with Iowa, Kentucky, Michigan, and Wisconsin.⁷ Under these agreements:

• Illinois residents working in reciprocal states: only pay Illinois income tax on wages, salaries, tips, and commissions earned in those states — not the other state's income tax. File an exemption form (e.g., Iowa Form 44-016) with your employer to avoid dual withholding.
• Residents of Iowa, Kentucky, Michigan, or Wisconsin working in Illinois: are exempt from Illinois income tax on wages and salaries. File IL-W-5-NR with your Illinois employer.

Important limitation: reciprocity applies only to wages, salaries, tips, and commissions. It does not apply to RSU vests, capital gains, or other investment income. A Wisconsin resident who works in Illinois and also vests RSUs in an Illinois-based job owes Illinois tax on those RSU vests — the reciprocity agreement does not shelter equity compensation income, only wages.

This is a meaningful distinction for remote workers and hybrid employees who live across state lines from their Chicago employer.

Planning strategies for Illinois tech employees

1. Model ISO exercises without state AMT budget

If you're a startup employee or pre-IPO engineer in Chicago with ISOs, Illinois' absence of a state AMT meaningfully expands your exercise capacity. The federal AMT exposure on ISO bargain elements is real and requires careful modeling — the ISO AMT calculator finds the maximum shares exercisable with zero federal AMT, and identifies your minimum tax credit carryforward when full AMT-free exercise isn't possible. But you don't need to reserve an additional 7% state AMT budget the way California employees do. An exercise strategy optimized purely for federal AMT efficiency doesn't leak to the state in Illinois.

2. Plan for the Illinois estate tax gap — especially if married

If your Illinois estate is approaching $8 million — or likely to cross it as RSU grants continue to vest and appreciate — work with an estate attorney to structure your documents before the first spouse dies. A bypass trust (also called a credit shelter trust or AB trust) that intentionally funds $8M of assets into a separate trust at first death can effectively double the couple's Illinois estate tax protection to $16M. Simple "everything to my spouse" wills don't accomplish this because they forfeit the first spouse's Illinois exemption. Illinois does not allow the portability election that the federal system provides.

3. No state AMT — but no LTCG preference either

Unlike Washington or Texas (no state income tax) and unlike states with preferential LTCG rates, Illinois is neutral: your RSU vest and your RSU appreciation face the same 4.95% rate. The federal incentive to hold RSU shares for 12+ months is real (converting ordinary income rates to 0/15/20% LTCG rates on post-vest appreciation). Illinois adds no additional incentive or disincentive. Concentration risk management and federal tax planning should drive the hold-versus-sell decision; Illinois doesn't move the needle.

4. Max 401(k) and Mega Backdoor Roth to reduce Illinois taxable income

Traditional 401(k) deferrals reduce Illinois taxable income dollar-for-dollar at 4.95% (the same mechanism as federal). The 2026 401(k) deferral limit is $24,500 ($32,500 if 50+ or $35,750 for the ages 60-63 super-catch-up). Illinois conforms to this federal deduction. Mega Backdoor Roth contributions are made with after-tax dollars — no Illinois deduction now, but tax-free withdrawals later. The Mega Backdoor Roth calculator shows how much contribution space you have above the standard deferral limit.

5. DAF for appreciated employer stock

Donating RSU shares (held 12+ months from vest) directly to a donor-advised fund eliminates the federal capital gains event and the Illinois 4.95% capital gains tax. You receive a federal charitable deduction at full fair market value. For Illinois tech employees with concentrated employer stock and charitable intent, this is the most tax-efficient way to reduce position size without paying capital gains. The DAF strategy guide covers implementation mechanics, including lot selection and the OBBBA rules on deductions for stock donations.

6. Track CA long-arm sourcing on pre-move grants

If you relocated from California to Illinois, your pre-move RSU and stock option grants may still carry California-source income for the California-apportioned portion of remaining vest tranches. The interaction of California long-arm sourcing with Illinois income tax is not straightforward and requires calculating grant-to-vest day counts for each active grant. A tax advisor who handles multi-state equity compensation can model the net liability and ensure you're claiming appropriate credits to avoid double-state-tax on the same income.

What a fee-only advisor can help you model

• Year-by-year ISO exercise strategy leveraging Illinois' zero-state-AMT environment, including federal AMT credit carryforward optimization
• Estate plan restructuring (bypass trust vs. simple will) to preserve both spouses' $8M Illinois exemptions
• Whether California long-arm sourcing still applies to your specific grants after a California-to-Chicago move, and what credit offsets are available
• RSU lot selection and tax-loss harvesting in a 4.95% state-tax environment
• Retirement account stacking (401k + Mega Backdoor Roth + HSA) to reduce Illinois ordinary income in peak earning years
• Concentrated stock risk reduction via systematic selling, 10b5-1 plans, or DAF donations of appreciated employer shares
• How reciprocity agreements interact with equity compensation if you live in Wisconsin, Iowa, Michigan, or Kentucky and work for an Illinois-based company