What it means
The US tax code carries a remarkable gift for startup investors: under Section 1202, gains on qualified small business stock can be excluded from federal tax, in whole or in part, after a minimum hold. For stock acquired after September 27, 2010 and on or before July 4, 2025, the exclusion can reach 100% after a five-year hold, capped per issuer at the greater of $10 million or ten times basis.
Later legislation changed the rules for stock acquired after July 4, 2025, adding partial exclusions of 50% at three years and 75% at four years, with 100% at five years, a higher cap of $15 million (or ten times basis) and a higher asset limit of $75 million. The qualifications are demanding, and the main tests are easy to miss.
The issuer must be a domestic C corporation, its gross assets must stay under $50 million when the stock is issued ($75 million for stock acquired after July 4, 2025), and the company must run an active qualified business, not services like law or finance. The investor must acquire the stock at original issue, directly from the company, for money, property, or services, and purchases from another shareholder do not qualify.
The fine print matters: the active business requirement, the holding period and the per-issuer caps have all been the subject of IRS technical guidance. Redemption rules police gaming, since significant company buybacks around the issuance can taint the stock, because Congress wanted the benefit to reward fresh capital, not churned cap tables.
Founders, angels, and venture funds plan around QSBS deliberately, since choice of C corporation over LLC, timing of rounds, and holding periods are all shaped by the exclusion's enormous value. For a non-finance reader, QSBS is the tax code's bet on startups: build a real operating company, hold the stock long enough, and the federal government may waive its share of the win.
State tax treatment can differ from the federal rules. Documentation decides audits years later.
Investors keep subscription agreements, cap tables, and asset certifications from issuance, because the holding-period and asset tests are examined when the gain is reported, not when the stock is bought. Stacking strategies multiply the benefit, since trusts and gifts can spread the per-issuer cap across taxpayers, a planning frontier that sophisticated founders now raise in the earliest rounds.
In practice
Real-world examples.
Example
A founder excludes $8 million of gain after selling stock in her qualified C corporation held six years. The gain is under the per-issuer cap, so the full amount is excluded. The checklist was the product.
Example
An angel verifies original-issue status before investing, knowing shares bought from existing holders never qualify for the exclusion. She asks for the company's asset certificate and keeps the subscription agreement. Years later the paperwork supports her claim.
Example
A startup's large share buyback is reviewed for the redemption rules that could taint recent QSBS issuances. The company's lawyers check the timing against new share issues. The buyback is restructured to avoid a problem.
Formula
Calculation
Exclusion up to 100% of gain, capped per issuer at the greater of the dollar cap ($10 million, or $15 million for stock acquired after July 4, 2025) or 10 times adjusted basis. Requirements: C corporation, gross assets under the applicable limit at issuance, original issue, the holding period, active qualified business.
Worked example. A fictional investor pays $250,000 for stock acquired in 2019 and sells it after six years for $4,500,000.
- Gain = $4,500,000 - $250,000 = $4,250,000.
- Cap = the greater of $10,000,000 or 10 x $250,000 = $2,500,000, so the cap is $10,000,000, and the gain is below it.
- With a 100% exclusion, the excluded gain is $4,250,000. At an assumed 20% federal long-term capital gains rate, the tax avoided is 0.20 x $4,250,000 = $850,000.
- For comparison, a fictional sale of post-July 2025 stock after four years with the same $4,250,000 gain would qualify for a 75% exclusion: $4,250,000 x 0.75 = $3,187,500 excluded, leaving $1,062,500 taxable.Case study
Seen in the real world.
This case study is fictional and illustrative. A made-up angel investor in Colorado puts $250,000 into a robotics startup's seed round in 2019. The company is a Delaware C corporation with $8 million in assets, running an active manufacturing business, and her shares come straight from the company's treasury at original issue. Her attorney confirms the QSBS boxes at the time and files the memo.
Six years later an acquirer buys the company, and her stake returns $4.5 million. Because the stock met every Section 1202 condition and cleared the five-year clock, her entire $4.25 million gain is excluded from federal tax under the 100% tier, saving roughly $850,000 at a 20% federal long-term capital gains rate. Her co-investor, who bought the same shares secondhand from a departing founder, pays full federal tax on an identical cheque, the original-issue rule making the difference. At a venture conference she now tells the story as a checklist rather than a windfall: the benefit was manufactured in 2019 by corporate form, issuance mechanics, and patience, and nobody involved found any of it accidental.
Watch out
Common mistakes.
- Assuming any startup stock qualifies; the issuer must be a C corporation under the applicable asset limit, such as $50 million for older stock, running a qualified active business at issuance. The form must precede the funding.
- Buying secondhand and expecting the exclusion; only original-issue stock acquired from the company itself counts.
- Forgetting the holding period; selling early forfeits the exclusion for stock acquired on or before July 4, 2025, while later stock earns only a partial exclusion at three or four years, and the clock runs from actual issuance, not commitment.
Questions
People also ask.
What is qualified small business stock?
Stock in a qualifying small C corporation whose gains can be excluded from federal tax, up to 100% after a five-year hold, under Section 1202.
What are the main conditions?
Domestic C corporation, gross assets under the applicable limit at issuance, original-issue acquisition, active qualified business, and the required holding period.
Is there a cap on the exclusion?
Yes; per issuer, the greater of the dollar cap ($10 million for older stock, $15 million for stock acquired after July 4, 2025) or ten times the investor's adjusted basis in the stock.
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