If you founded a startup or joined as an early employee at a US C-corporation, Qualified Small Business Stock (QSBS) under Internal Revenue Code §1202 is potentially the single most valuable tax provision in the code for you. Stock that meets the §1202 qualification can be sold with up to 100% of the gain excluded from federal income tax, capped at the greater of $10 million or 10× your tax basis per issuer. On a $9M founder exit that’s typically a $1.8–$2M federal tax savings — but only if the stock qualifies and you held it long enough.
This is one of those tax provisions that almost looks too good to be true. It survived multiple Congressional repeal attempts and was made permanent by the PATH Act of 2015. Here’s exactly how to qualify and what the calculator behind the curtain checks.
The headline benefit
Under IRC §1202(a), a non-corporate taxpayer who holds qualified small business stock for more than 5 years and sells it can exclude a percentage of the gain from gross income:
| Stock acquired | Exclusion % | Effective rate |
|---|---|---|
| Before Aug 11, 1993 | 0% | Standard LTCG |
| Aug 11, 1993 – Feb 17, 2009 | 50% | ~14% (with 7% AMT preference) |
| Feb 18, 2009 – Sep 27, 2010 | 75% | ~7% (with 7% AMT preference) |
| After Sep 27, 2010 | 100% | 0% federal |
Stock acquired at original issuance after September 27, 2010 — and held for 5+ years — qualifies for the 100% exclusion with no AMT preference. That’s a complete federal income-tax holiday on the capped portion of the gain.
The cap: $10 million OR 10× basis
The exclusion is capped at the greater of:
- $10,000,000 lifetime cap per issuer (reduced by aggregate prior excluded gain from the same issuer), OR
- 10× the aggregate adjusted basis of qualifying stock disposed of by the taxpayer during the year
A founder with $1,000 of basis in a startup that sells for $50M would get $10M excluded ($10M cap > 10× $1,000 = $10,000). An employee who exercised stock for $500,000 and sees it sell for $20M gets the larger of $10M cap vs $5M (10× basis) = $10M excluded, leaving $9.5M of taxable gain. The 10× basis test only beats the $10M cap when basis is over $1M.
The $10M cap is per issuer per taxpayer. A founder holding stock in three separate qualifying companies has three separate $10M caps. And a married couple filing jointly has $10M per spouse if each holds qualifying stock — but careful: the cap is per taxpayer, so transferring stock to a non-spouse to “stack” caps doesn’t work (the §1202 holding period and original-issuance attributes don’t transfer).
The qualification tests
Stock qualifies as QSBS only if all of the following are true:
1. Domestic C-corporation
The issuer must be a domestic C-corp at the time the stock is issued AND at all times during substantially all of the holder’s holding period. LLCs, S-corps, and partnerships do not qualify at the entity level. If your startup converts from an LLC to a C-corp, the QSBS clock starts at the conversion date — not at the original LLC formation.
If the company converts from C-corp to S-corp during your holding period, you lose QSBS qualification on the conversion date. (You can still use the gain exclusion for the period it was a C-corp under certain conditions — see Treas. Reg. §1.1202-2.)
2. Original-issuance acquisition
You must acquire the stock at original issuance from the corporation in exchange for money, property (other than stock), or services to the corporation. Buying QSBS-eligible stock on the secondary market does not give the buyer §1202 status — the new owner starts with non-QSBS basis. Two narrow exceptions: (a) gifts, inheritance, and certain partnership distributions can transfer QSBS status under §1202(h); (b) §351 incorporation transactions where qualifying stock is exchanged for the new corp’s stock can preserve the §1202 attributes.
3. $50 million aggregate gross assets test
At all times before AND immediately after the issuance, the corporation’s aggregate gross assets must not exceed $50 million. “Aggregate gross assets” means the cash plus other property held by the corporation, valued at adjusted basis (or fair market value if the property was contributed to the corp). The $50M test is checked at issuance — once the company crosses $50M, previously-issued stock remains qualified (the limit doesn’t retroactively disqualify), but newly-issued stock from that point forward is not QSBS.
This is why early employees benefit most: the cap is tested against company size at the time of stock issuance. A founder issued shares at incorporation when the company had no assets clearly qualifies. An employee who joins after a $30M Series B and gets options issued when the company has $35M of cash + IP — also qualifies. An employee joining after a $100M Series D — does not.
4. Active business in a qualified trade
At least 80% of the corporation’s assets must be used in the active conduct of one or more qualified trades or businesses. §1202(e)(3) explicitly disqualifies certain trades:
- Health (medical, dental, veterinary)
- Law, engineering, accounting, actuarial science, performing arts, consulting, athletics, financial services, brokerage services
- Banking, insurance, financing, leasing, investing, or similar businesses
- Farming (including raising or harvesting trees)
- Production or extraction of products from oil, gas, mining
- Hotel, motel, restaurant, or similar lodging/food businesses
Most software, biotech, hardware, and consumer-product C-corps pass this test cleanly. Service businesses (consulting, financial advisory) generally do not.
5. Five-year holding period
The stock must be held by the same taxpayer (or transferee with carryover basis) for more than 5 years before sale. There is no “qualified disposition” carve-out for shorter holding periods — under 5 years there is no §1202 exclusion at all, even partial.
If you sell at year 4 and 11 months, you get nothing. The taxpayer who holds five years and one day gets the full 100% exclusion (assuming all other tests pass).
§1045 rollover: the partial fix for under-5-year sales
If you must sell QSBS before the 5-year mark, IRC §1045 lets you roll the gain into another QSBS investment within 60 days and defer recognition. The rolled basis carries forward, and the holding periods aggregate (with some technical limits). This is how some serial entrepreneurs maintain QSBS treatment across multiple ventures.
State conformity: where QSBS is fully respected vs not
Federal §1202 exclusion does not bind state income tax. States vary widely:
- Conform fully (federal exclusion = state exclusion): most states with income tax that follow federal AGI as the starting point. Includes most red and purple states.
- Decoupled — no QSBS exclusion: California, New Jersey, Pennsylvania, Mississippi, Alabama (situational), and a handful of others tax the full federal-excluded gain at state ordinary or capital gain rates. California is the biggest single non-conformer for tech founders — the state will tax 100% of a federally-excluded gain at its ~13.3% top bracket.
- No income tax: Texas, Florida, Washington, Nevada, etc. — irrelevant whether they conform; no state tax either way.
For founders considering pre-IPO state moves, the QSBS conformity gap is one of the biggest single-line items: a $9M federal-excluded gain in California still costs ~$1.2M in state tax; the same gain in Texas costs $0.
Common QSBS mistakes
Skipping the §351 documentation on incorporation conversion. When converting an LLC to a C-corp pre-Series A, the conversion documents must explicitly preserve the QSBS attributes via §351 exchange treatment. If your law firm doesn’t do this correctly, the QSBS clock starts later than it should.
Repurchase by the corporation within 2 years. §1202(c)(3) disqualifies stock if the issuing corporation engages in significant redemptions (buyback) within 2 years of issuance. If your startup does a tender offer, that can taint QSBS for the entire share class issued in that window. Founders sometimes also accidentally trip this with founder-share buybacks during early funding rounds.
Failing to document the $50M asset test. The corporation should produce an asset roll-forward at each issuance event. If the IRS challenges QSBS years later at sale, you’ll need contemporaneous evidence that aggregate gross assets stayed under $50M through the issuance date. Most early-stage CPA firms don’t produce this without being asked.
Mixing QSBS and non-QSBS stock. If you hold both qualifying and non-qualifying stock in the same issuer (e.g., some shares acquired at original issuance and others bought on the secondary market), you must track basis and acquisition date by lot. The IRS does not let you cherry-pick which lot you sell.
OBBBA-era updates (2026)
The One, Big, Beautiful Bill Act (P.L. 119-1, July 2025) modified several aspects of §1202. Specific changes are technical and the regulations are still being interpreted; consult your CPA on whether the OBBBA changes affect your specific situation. Material changes likely include adjustments to the dollar thresholds and clarification of the qualified-trade tests. The pre-OBBBA framework described above remains the foundation; OBBBA tightens or loosens specific edges. The QSBS Calculator reflects the current framework and is updated as Treasury issues guidance.
Key takeaways
- §1202 excludes up to 100% of gain on QSBS held 5+ years, capped at greater of $10M or 10× basis per issuer
- Original-issuance acquisition only — buying QSBS-eligible stock on the secondary market does not transfer the benefit
- C-corp domestic issuer, $50M aggregate gross asset ceiling at issuance, active qualified trade or business
- Most professional-services trades disqualify (law, finance, consulting, healthcare); most software/biotech/hardware C-corps qualify
- 5-year holding period is binary — under 5 years there’s no exclusion at all, only §1045 rollover relief
- California, NJ, PA, MS do not conform — state-level tax planning is independent of the federal exclusion
- Document the §351 conversion, the $50M asset test at each issuance, and the original-issuance status — these are the audit attack points
Run your specific scenario in the QSBS Calculator — it computes the federally-excluded portion, the residual taxable gain, and the state-tax surcharge in non-conforming states.