Illinois has officially changed its treatment of Qualified Small Business Stock (QSBS), marking an important development for founders, investors, and business owners with Illinois tax exposure.
For years, Illinois generally followed the federal treatment of Section 1202, meaning taxpayers who qualified for the federal QSBS exclusion could often exclude the same gain for Illinois income tax purposes. That approach is now changing.
Through Senate Bill 3019, Public Act 104-0468 became effective July 1, Illinois enacted legislation requiring taxpayers to add back gain excluded from federal gross income under Section 1202. The change applies to tax years ending on or after December 31, 2026, meaning it is already in effect for taxpayers with 2026 gains.
The Illinois Department of Revenue explains that
“for tax years ending on or after December 31, 2026, Illinois decouples from Internal Revenue Code (IRC) Section 1202, requiring individuals, trusts and estates, and partnerships to add back any federally excluded Qualified Small Business Stock (QSBS) gains to their Illinois base income or loss.”
The change effectuates the change by modifying the definition of base income for individuals in 35 ILCS Section 203 to include an add-back the gain amounts related to the QSBS exclusion taken at the federal level by adding paragraph D-26:
“For taxable years ending on and after December 31, 2026, an amount equal to the amount of gain excluded from gross income under Section 1202 of the Internal Revenue Code.”
This means that even if a taxpayer qualifies for the federal QSBS exclusion, the same gain may no longer be excluded from Illinois taxable income, and thereby subject to capital gains tax of approximately 5%.
Why This Matters
Section 1202 is one of the most valuable tax benefits available to founders and early investors in qualifying C corporations. At the federal level, eligible taxpayers may be able to exclude up to 100 percent of gain from the sale of QSBS, subject to certain limitations and holding period requirements.
Recent federal changes expanded the value of QSBS by increasing the per-issuer exclusion amount, raising the gross asset threshold for qualifying corporations, and creating a tiered exclusion structure for certain stock held for at least three or four years.
As the federal benefit has become more generous, states have had to decide whether to continue following the federal exclusion or decouple from it. Illinois has now chosen to decouple.
The Illinois Add-back
The new Illinois law requires an additional modification for the amount of gain excluded from federal gross income under Section 1202. In practical terms, this means taxpayers must add the federally excluded QSBS gain back when calculating Illinois income.
For Illinois taxpayers, the result can be significant. A transaction that produces no federal income tax on qualifying QSBS gain may still create Illinois income tax liability.
This change is especially important for taxpayers who are planning a QSBS sale, have already completed a sale in 2026, or are evaluating the after-tax impact of a future exit.
Illinois Joins Other Nonconforming States
Illinois now joins a group of states that do not fully recognize the federal Section 1202 exclusion. Historically, states such as California, Alabama, Mississippi, and Pennsylvania have not conformed to the federal QSBS exclusion; however, as a result of the Federal QSBS expansion in 2025 from enactment of OBBBA, additional states have “decoupled” from 1202, adding to the list Oregon, Washington State, Washington DC, and now Illinois.
This reinforces an important planning point: QSBS analysis should never stop at the federal level. As one recent tax planning commentary observed,
“Whenever Section 1202 is in play, tax practitioners should determine whether the Section 1202 exclusion is available (in full or in part) in the applicable jurisdiction.”
Illinois’ recent legislation is another reminder that state conformity can materially affect the overall tax savings from a transaction.
A taxpayer may qualify for the full federal exclusion but still owe state income tax depending on the jurisdiction involved.
Planning Considerations
For business owners and advisors, Illinois’ decoupling makes state tax planning even more important.
Taxpayers with Illinois residency, Illinois-source income, pass-through interests, or trust structures connected to Illinois should carefully review how the new law may apply. The timing of a sale, the taxpayer’s residency, the source of the gain, and the structure of the investment may all become more important in determining the ultimate tax result.
The change also highlights the need to monitor state conformity regularly. As Section 1202 becomes more valuable at the federal level, more states may evaluate whether they want to continue conforming to the exclusion.
Looking Ahead
Illinois’ decision to decouple from Section 1202 reflects a broader tension between federal tax incentives and state revenue concerns. While Congress has expanded the federal QSBS benefit to encourage investment in small businesses, states are not required to provide the same tax benefit – and budget constraints may prompt them to no longer do so.
For founders, investors, and business owners, the takeaway is clear: QSBS can still provide substantial federal tax savings, but state conformity must be reviewed before assuming the entire gain will be tax-free.
Illinois’ new add-back rule makes that analysis especially important for taxpayers with Illinois connections. Going forward, taxpayers considering a QSBS sale should evaluate both federal eligibility and state-level tax consequences early in the planning process.
This article does not constitute legal or tax advice. Please consult with your legal or tax advisor with respect to your particular circumstance.