Section 1202's gain exclusion is simultaneously more valuable and more contested than it has been at any point in its 33-year history. The One Big Beautiful Bill Act, signed in 2025, raised the per-taxpayer, per-issuer cap from $10 million to $15 million for qualified small business stock issued after July 4, 2025, per analysis published in Tax Notes Federal on September 7, 2026.1 At the same time, Treasury officials are preparing guidance aimed at the trust-stacking strategies that sophisticated investors use to multiply that exclusion across a single family structure, with the assistant secretary for tax policy stating publicly in May 2026: "Let me just warn you: we don't like stacking."2
What the Exclusion Actually Does, and What It Now Permits
Section 1202 provides that a taxpayer other than a corporation is exempt from tax on up to 100% of the gain from a sale of qualified small business stock, defined as stock in a domestic corporation that satisfies certain qualifications, including having assets below a certain threshold both before and after the stock issuance. The taxpayer must have acquired the stock at original issuance.
Section 1202 currently caps a taxpayer's gain exclusion at the greater of $15 million (or $10 million for stock acquired before July 4, 2025) and ten times the taxpayer's basis in the stock. The 10x-basis alternative matters most to investors who paid material sums at issuance: a $5 million basis creates a $50 million potential exclusion that dwarfs the dollar cap entirely, and that calculation runs separately per taxpayer.3 For stock acquired after July 4, 2025, the seller must hold the stock for at least three years to exclude 50% of the gain, at least four years to exclude 75%, and at least five years to exclude 100%.
The structural consequence is significant. The exclusion limits are per-taxpayer, per-issuer, which means multiple family members can each claim their own exclusion for stock from the same company. At $15 million per holder, a family of five working from the same cap table position can shelter $75 million in gain before the 10x-basis alternative even enters the calculation.
How Stacking Operates and What Makes It Work
Because the limitation under Section 1202(b) applies to each specific "taxpayer," a single founder can multiply their excludable gain by transferring stock to separate taxpayers prior to a liquidity event. The primary vehicles used in a stacking strategy are irrevocable non-grantor trusts. The IRS recognizes a non-grantor trust as a separate and distinct taxpayer from the person who created it; because it is a separate taxpayer, the trust qualifies for its own, separate gain exclusion.
The mechanics of gifting do not reset the clock. Section 1202(h) lets someone who receives stock by gift step into the donor's shoes, keeping the stock's qualified status and the donor's holding period. That tacking provision is what makes the strategy operable in practice: shares gifted into a trust years before a sale carry both the original qualified status and the accumulated holding period, preserving eligibility for the full 100% exclusion at the five-year mark.
Stacking clearly makes sense when anticipated gain substantially exceeds the per-taxpayer cap. If a holder is sitting on $30 million or more in unrealized gains, the federal tax savings from even two additional trusts dwarf the setup costs. Below roughly $12 million to $15 million in total gain, the personal exclusion and a spouse's exclusion likely cover the position, and the legal and administrative costs of additional trust structures are difficult to justify.4
There are two practical limits that the dollar headline obscures. First, stacking is a federal benefit only. States that do not conform to Section 1202, including California, still tax the gain. Second, each gift of appreciated shares consumes lifetime gift tax exemption, which currently stands at $15 million (2026), creating a direct tradeoff between income tax savings and transfer-tax capacity that requires case-specific modeling before the structure is built.4
Where Treasury's Scrutiny Is Actually Aimed
Treasury Assistant Secretary for Tax Policy Kenneth Kies told a tax conference on May 20, 2026: "Let me just warn you: we don't like stacking." A second Treasury official made similar comments on May 9, and the Wall Street Journal reported on June 29 that Treasury and the IRS were preparing guidance.
The concern is specific, not categorical. Per that reporting, ordinary family estate planning appears less likely to be targeted; Treasury's stated concern is overlapping or synthetic trusts that multiply exclusions for the same economic beneficiaries. According to reporting, the assistant secretary indicated that Treasury was focused on investors who go beyond the ordinary one-trust-per-family-member planning model, although the timing and scope of any guidance remain uncertain.
Academic commentary has sharpened that line. Gregg Polsky (NYU) and Ethan Yale (UVA), writing in Tax Notes Federal on September 7, 2026, argue that the government's existing tools are inadequate to the problem and call on Treasury to promulgate new regulations.1 Section 643(f) permits multiple trusts to be treated as one where they have substantially the same grantor and primary beneficiary and a principal purpose of tax avoidance. But that rule requires a facts-and-circumstances showing that is difficult to make against structures with genuinely distinct beneficiaries.
As of September 21, 2026, no proposed or final regulation, notice, or revenue ruling specifically addressing trust stacking has been issued. The strategy is permissible under current law. The open question is whether guidance, when it arrives, will apply prospectively only or whether it will reach structures already in place.
The Planning Implication
The asymmetry in the current environment is straightforward: the exclusion is larger than it has ever been, the strategy to multiply it is legally intact, and the regulatory signal is the clearest it has been in Section 1202's history without yet producing a rule. A plan built early, with independent trustees, distinct beneficiaries, qualified appraisals, and a purpose that stands without the tax result, remains one of the most valuable tools available to a founder's family. Structures that cannot survive that description on their own terms carry regulatory exposure that is difficult to price and impossible to fully hedge after the fact.