QSBS gives millions tax-free. Five ways to lose it anyway.

The exclusion (defined under IRC §1202) zeros out federal capital-gains tax on millions of dollars of stock gain. The catch: five specific ways to lose it.

QSBS doesn't shrink the tax. It deletes it. Five mistakes put it back.

The five most expensive QSBS mistakes

Each of these five erases part or all of the exclusion you were on track to receive.

1. Selling before the five-year mark. Under the OBBBA rules (stock acquired after July 4, 2025), partial exclusions kick in earlier: 50% at three years, 75% at four years, 100% at five. For stock acquired before OBBBA, anything short of a full five-year hold gets you nothing. A sale at four years and 11 months on pre-OBBBA stock saves you zero federal tax under §1202. The checker tells you how many months you have left to the next tier.
2. Buying the stock on the secondary market. Only original-issuance stock qualifies: shares you acquired directly from the company at issue. Buying QSBS-eligible stock from another shareholder (a tender offer, a private secondary, a SecondMarket-style transaction) breaks the chain. The narrow exception is stock received by gift or inheritance, which tacks the original holder's status and five-year clock.
3. Working in a disqualified trade or business. §1202 carves out services-heavy sectors. Disqualified industries include law, accounting, consulting, financial services, health services, engineering, architecture, hospitality, and performing arts. Software, manufacturing, biotech R&D, retail, and wholesale qualify. If your C-corp's primary revenue isn't from a qualified trade or business, neither is its stock, no matter how long you hold it.
4. Ignoring state non-conformity. The federal exclusion is generous; not every state follows along. California, Alabama, Mississippi, and Pennsylvania do not conform to §1202: you owe full state tax on the gain the IRS just excluded. New Jersey now conforms for sales in tax years 2026 and later, not before. Hawaii caps the exclusion at 50%, and Massachusetts has narrower conformity than federal. The state bill on a federally excluded $10 million gain can run $900K to $1.3M in California or New Jersey (pre-2026).
5. Missing the 10x-basis cap interaction. The dollar cap is the greater of the per-issuer ceiling ($10 million for pre-OBBBA stock, $15 million for OBBBA stock) or 10× your adjusted basis in the stock. Founders with near-zero basis are capped at the dollar ceiling. Later-stage employees who paid real money at exercise, or held capitalized founder loans converted to stock, can exclude many multiples of $10 million if their basis times ten exceeds the ceiling. Forgetting the 10x branch leaves real exclusion on the table.

What §1202 actually does

Section 1202 lets a non-corporate shareholder exclude federal capital-gains tax on the sale of stock that qualifies as Qualified Small Business Stock. The exclusion is capped per shareholder per issuer (each company you hold QSBS in counts separately). At the federal long-term capital-gains rate of 20% plus the 3.8% Net Investment Income Tax (NIIT), every dollar excluded saves 23.8¢ in federal tax. A full $10 million exclusion is $2.38 million in federal tax avoided; the $15 million OBBBA cap pushes the maximum federal saving to $3.57 million per issuer per shareholder.

The four acquisition eras

§1202 has been amended several times. The exclusion percentage and dollar cap depend on when you acquired the stock, not when you sell it.

• Aug 11, 1993 – Feb 17, 2009. 50% exclusion at five-year hold. 7% of the excluded portion is an Alternative Minimum Tax (AMT) preference item, so the effective federal benefit is smaller than 50% would suggest.
• Feb 18, 2009 – Sep 27, 2010. 75% exclusion at five-year hold. Same 7% AMT preference on the excluded portion.
• Sep 28, 2010 – Jul 4, 2025. 100% exclusion at five-year hold. No AMT preference. This is the era most current QSBS sales fall into: stock issued during the post-2010 startup boom is now well past its five-year mark.
• Jul 5, 2025 onward (OBBBA). Tiered exclusion: 50% at three years, 75% at four years, 100% at five years. No AMT preference. Per-issuer dollar cap raised from $10M to $15M, and the aggregate gross asset ceiling raised from $50M to $75M. Both new caps are indexed to inflation starting in 2027.

The eight qualification tests

Stock qualifies as QSBS only if every one of these is true:

1. US C-corporation. The issuer must be a domestic C-corp. S-corps, LLCs, partnerships, and foreign entities cannot issue QSBS.
2. Original-issuance acquisition. You acquired the stock directly from the company (founder shares, an exercise of an option or warrant, a primary funding round, a stock-grant plan). Gifts and inheritances tack the original holder's status.
3. Qualified trade or business. The company's primary revenue is not in the disqualified-industry list (services-heavy fields, extractive industries, hospitality, etc.).
4. Active business requirement. The company must use at least 80% of its assets in the active conduct of a qualified trade or business. Cash hoards and passive investments above that threshold can disqualify the stock.
5. Gross asset cap at issuance. The company's aggregate gross assets must have been under $50 million (or $75M for OBBBA stock) at the time the stock was issued, including immediately after issuance. Once the company crosses the cap, future issuances don't qualify, but stock issued before the crossing remains QSBS-eligible.
6. Five-year hold (or OBBBA tier). You held the stock for at least five years (pre-OBBBA), or at least three years (OBBBA, for partial exclusion).
7. Non-corporate shareholder. §1202 exclusion applies to individuals, trusts, and pass-through entities. Corporate shareholders cannot claim the exclusion.
8. No disqualifying redemptions. Significant company redemptions of stock from the shareholder or related parties around the issuance date can disqualify the stock. The rules look at a four-year window (two years before to two years after issuance).

The cap: per-issuer dollar ceiling OR 10x basis

The exclusion is capped at the greater of two limits, applied per shareholder per issuer:

• Dollar cap. $10 million for pre-OBBBA stock; $15 million for OBBBA stock. Indexed to inflation starting 2027 (OBBBA only).
• 10× adjusted basis. Ten times the stock's adjusted basis at the time of issuance. Founders who paid pennies per share land near zero on this branch. Employees who exercised priced options or purchased shares at fair value can land in the millions or tens of millions.

State conformity is the silent half of the math

Federal §1202 is settled law. Whether your state taxes the federally excluded gain is a separate question, and the answer varies.

• Non-conforming. California, Alabama, Mississippi, and Pennsylvania tax the full gain at the state level. California's top long-term rate is 13.3%, so a $10 million federal exclusion leaves a $1.33 million California bill. Pennsylvania's flat 3.07% leaves $307K.
• New Jersey: changed in 2026. NJ did not conform for tax years through 2025. NJ adopted §1202 (including OBBBA enhancements) for tax years beginning on or after January 1, 2026. The sale date determines which set of rules apply.
• Partial conformity. Hawaii allows only a 50% exclusion regardless of what federal law allows. Massachusetts conforms more narrowly than federal in ways that benefit the taxpayer less; check state guidance before relying on the federal number.
• Full conformity. Most other states (including New York, Washington, Texas, Florida, and the 30+ states that follow federal treatment) honor the §1202 exclusion in full.

Stacking exclusions across family

Each shareholder gets their own per-issuer cap. Married couples filing jointly count as one shareholder, but adult children, parents, and trusts each get their own caps. Gifting QSBS shares to family members (or to trusts for their benefit) before sale can multiply the exclusion the family captures in aggregate. The gifted shares retain the original holder's basis and acquisition date, so the five-year clock keeps running without interruption.

This planning is intricate and depends on gift-tax exposure, state-residency considerations, and the specific terms of any trusts involved. The point of mentioning it here is to flag that QSBS exclusion is not necessarily capped at one $10M-$15M per company per household. Work with a tax attorney before moving shares.

Special cases worth knowing about

§1045 rollover: extend the clock without restarting it

If you sell QSBS before the five-year mark, you can defer the gain by rolling the proceeds into new QSBS within 60 days under IRC §1045. Your holding period in the original stock tacks onto the new stock, so a founder who sells at year four can roll into another qualifying issue and keep the clock counting toward five years total. Practical use cases: company sale with cash proceeds before your five years, or an exit from a position you want to exit but the §1202 benefit you want to preserve.

Conversion from S-corp or LLC: doesn't qualify

Stock you receive when an S-corp or LLC converts to a C-corp does not qualify as QSBS, even if the resulting C-corp would otherwise be QSBS-eligible. The original issuance had to be from a C-corp; the conversion does not retroactively make the prior holding qualify. This catches founders who started in an LLC for tax flexibility and converted later.

Hedging the position while waiting for the five-year mark

Holding for five years means accepting five years of single-stock concentration risk. Some founders and early employees hedge during the wait: a zero-cost collar on the underlying QSBS position can cap downside without selling and breaking the §1202 clock. The structure has its own §1259 constructive-sale risk for tight strike spreads: a hedge so tight that you've effectively sold the stock can trigger immediate taxation. Work with a CPA before layering hedges on QSBS.

Where to go from here

The QSBS Qualification Checker runs the eight tests against your specific stock and returns the verdict, the applicable cap (the greater of the dollar ceiling or 10× basis), the excludable gain in dollars, the federal tax you save, and a state conformity note. If the verdict is "qualifies," the next conversation is with a CPA who can confirm the qualification before the sale and prepare the §1202 election on Form 8949. If the verdict is "too soon," the checker tells you how many months you have left to the next exclusion tier.

For broader equity planning, the single-stock concentration risk article covers what to do about the position while you wait, and the AMT crossover article covers the interaction with ISO exercises (which often produce the QSBS shares in the first place).