Qualified Small Business Stock is the most valuable tax benefit most founders have never properly planned for. Handled correctly, Section 1202 of the Internal Revenue Code lets you exclude up to $15 million -- or, for some founders, far more -- of gain from federal income tax when you sell your startup. Handled carelessly, the same stock produces a fully taxable gain and a conversation with your accountant that nobody enjoys.
The benefit is enormous, the rules are technical, and almost everything that determines whether you qualify happens years before the exit. This guide covers what QSBS is, what the One Big Beautiful Bill Act changed in 2025, who qualifies, and the specific things founders get wrong while there is still time to fix them.
The Short Answer
QSBS is stock in a qualifying C corporation that, if you hold it long enough, lets you exclude a large portion -- often all -- of your capital gain from federal tax when you sell. The exclusion is per taxpayer, per company, and is the greater of $15 million or 10 times your basis in the stock.
"Section 1202" refers to the Internal Revenue Code provision that created the exclusion in 1993 to encourage investment in small businesses. For most of its history it was a niche benefit. A series of expansions -- culminating in the One Big Beautiful Bill Act of 2025 -- has made it one of the largest tax breaks available to anyone who builds or invests early in a startup.
The catch is that the qualification is determined by facts you set in motion at incorporation and at every financing: your entity type, the company's asset size, the nature of its business, and how long you hold the stock.
What the One Big Beautiful Bill Act Changed
This is the single most important update for any founder reading about QSBS in 2026, because the rules now depend on when you acquired your stock.
For QSBS acquired after July 4, 2025, the One Big Beautiful Bill Act (OBBBA) made three significant changes:
- A tiered holding period. You no longer have to wait a full five years for any benefit. You can now exclude 50 percent of gain after a three-year hold, 75 percent after four years, and 100 percent after five years.
- A higher per-issuer cap. The lifetime exclusion ceiling rose from $10 million to $15 million per company (still the greater of that figure or 10 times basis), indexed for inflation starting in 2027.
- A higher gross-assets ceiling. The company can now have up to $75 million in aggregate gross assets at the time the stock is issued, up from $50 million, which means later-stage companies remain QSBS-eligible for longer.
For QSBS acquired on or before July 4, 2025, the old rules still apply: a flat five-year holding period, 100 percent exclusion, a $10 million per-issuer cap, and a $50 million gross-assets ceiling. Nothing about the OBBBA changes retroactively shortens the clock on stock you already held.
The practical consequence: most stock issued at companies founded or financed from mid-2025 onward will fall under the more generous new regime, and you should track acquisition dates carefully because two tranches of the same company's stock can be governed by different rules.
For a broader walkthrough of the legislation, see our overviews of the One Big Beautiful Bill Act and tax planning under the new law.
The Five Tests That Determine Eligibility
For stock to be QSBS, every one of the following must be true. Miss any one and the exclusion is gone -- not reduced, gone.
1. C corporation. The issuer must be a domestic C corporation, both when the stock is issued and substantially throughout your holding period. LLCs, S corporations, and partnerships do not issue QSBS. This is one of several reasons venture-backed startups incorporate as Delaware C corporations from day one -- see how entity choice shapes founder pay and structure.
2. Original issuance. You must acquire the stock directly from the company in exchange for money, property, or services -- not bought from another shareholder on the secondary market. Founder shares, priced-round purchases, and stock acquired by exercising options all qualify. Buying shares from a departing employee generally does not.
3. Gross assets under the cap. The company's aggregate gross assets must not have exceeded the threshold ($50 million for older stock, $75 million under OBBBA) at any point before, and immediately after, your stock was issued. A company can blow past the cap later and your earlier stock stays qualified -- the test is measured at issuance.
4. Active business requirement. At least 80 percent of the company's assets must be used in the active conduct of a qualified trade or business. Most software, hardware, and consumer companies pass easily. Certain businesses are categorically excluded: health, law, accounting, consulting, financial services, brokerage, farming, hospitality, and any business where the principal asset is the reputation or skill of its employees.
5. Holding period. You must hold the stock for the required time -- three, four, or five years under OBBBA's tiers, or a flat five years under the old rules. The clock starts when you acquire the stock, which for option holders means the exercise date, not the grant date.
How Much You Can Actually Exclude
The exclusion is the greater of $15 million or 10 times your adjusted basis in the stock, per company, per taxpayer.
For most founders, basis is near zero -- you paid a fraction of a cent per share for founder stock -- so the $15 million figure controls. But the "10 times basis" alternative matters more than founders assume:
- If you exercise options and pay a meaningful strike price, or buy stock in a priced round, your basis rises. A $3 million basis unlocks a $30 million exclusion under the 10x rule.
- The cap is per company, so a serial founder accumulates a fresh ceiling with each qualifying company.
- The cap is per taxpayer, which opens legitimate planning: spouses each have their own cap, and so do certain non-grantor trusts. "QSBS stacking" -- gifting shares to multiple non-grantor trusts before an exit, each with its own exclusion -- is a well-established strategy for founders whose expected gain exceeds the individual cap.
A worked example: a founder holds stock with a $20,000 basis and sells for $16 million after five years under the new rules. The exclusion is the greater of $15 million or 10 times $20,000 ($200,000), so $15 million is excluded. The remaining roughly $1 million of gain is taxed as a normal long-term capital gain. Federal tax on $15 million of fully excluded gain: zero.
State Tax: The Asterisk That Surprises Founders
Section 1202 is a federal exclusion. States decide independently whether to conform.
California does not conform. A California founder who excludes $15 million federally still owes California tax -- up to 13.3 percent -- on the entire gain. New Jersey, Pennsylvania, Mississippi, and Alabama also diverge in various ways. Most other states follow the federal treatment.
For a California-based, venture-backed founder, this is not a footnote -- it can be a seven-figure difference. It is one of the reasons exit-timing and residency planning belong on the agenda years before a liquidity event, not in the quarter you sign a term sheet.
QSBS for Employees, Not Just Founders
QSBS is often discussed as a founder benefit, but early employees who exercise their options acquire original-issuance stock that can qualify on its own terms.
This is one of the strongest arguments for early exercising. An employee who exercises shortly after grant -- when the spread is small -- starts the QSBS clock early and converts what would have been ordinary income or short-term gain into potentially excludable QSBS gain. The interaction between early exercise, the 83(b) election, and QSBS is one of the highest-leverage pieces of personal tax planning available to a startup employee. We cover the 83(b) mechanics in our guide to how to pay yourself as a founder.
Section 1045: The Rollover Safety Valve
What happens if you need to sell before you hit the holding period -- in an acquisition, say, three years in under the old rules?
Section 1045 lets you roll over the proceeds from QSBS held more than six months into new QSBS within 60 days, deferring the gain and carrying your original holding period forward. It is the QSBS equivalent of a 1031 exchange. For a founder whose company is acquired before the clock runs, a 1045 rollover into another qualifying startup can preserve the benefit rather than forfeit it. The mechanics are unforgiving on timing, so plan the rollover before the sale closes, not after.
Common Mistakes
Incorporating as an LLC. The most expensive QSBS mistake happens at formation. An LLC issues no QSBS. Founders who form an LLC "to keep it simple" and convert to a C corporation later only start the QSBS clock -- and the gross-assets measurement -- at conversion, often after the company has already grown. The asset value at conversion becomes your basis, which can help the 10x calculation, but you lose years of holding period.
Letting gross assets quietly exceed the cap before a key issuance. If you are about to issue founder or employee stock and a large round is about to land, the sequence matters. Stock issued before the company crosses the asset threshold qualifies; stock issued after does not.
Buying secondary shares and assuming they qualify. Stock purchased from another shareholder is not original issuance and is not QSBS. Employees joining a secondary-heavy cap table should understand which of their shares qualify.
Redemptions that taint the stock. Certain stock redemptions by the company around the time of issuance can disqualify QSBS under anti-abuse rules. Significant buybacks deserve a tax review before they happen.
Failing to document. QSBS is claimed on your return, but the burden of proving eligibility is yours. You need the gross-assets figures at issuance, the original-issuance evidence, the entity history, and the holding-period dates. Assemble this in a dedicated file at issuance, not five years later when memories and records have faded.
What We Recommend
For founders and early employees:
- Confirm your entity is a C corporation and that your stock was acquired by original issuance. If you are still an LLC and venture financing is on the horizon, model the conversion now.
- Record the acquisition date and the company's gross assets for every tranche of stock you hold, and tag which OBBBA regime governs each.
- Consider early exercise to start the QSBS clock early, weighed against the cash and the AMT exposure on ISOs.
- If your expected gain exceeds $15 million, talk to a tax advisor about stacking through non-grantor trusts before -- not after -- a term sheet is signed.
- If you are in California or another non-conforming state, put state exposure on the table early; it changes the math materially.
QSBS planning is most valuable years before the exit, when the inputs are still under your control. We help founders structure entity, equity, and exit decisions so the Section 1202 benefit is preserved by the time it matters. If you want to confirm your stock qualifies -- or fix the structure while you still can -- book a free consultation and we will walk through your specific cap table.
This article is general information, not tax or legal advice. QSBS qualification is fact-specific; confirm your situation with a qualified advisor before acting.
