Two founders sell the same amount of stock. One owes nothing in federal capital gains tax. The other owes six figures to the IRS. The difference is rarely luck. It comes down to whether their stock was structured to qualify for the Section 1202 exclusion from the very beginning.
What Is QSBS for Founders?
Qualified Small Business Stock, or QSBS, is stock issued by an eligible US C-corporation that can qualify for a federal capital gains tax exclusion under Section 1202 of the Internal Revenue Code. For founders, it is one of the most valuable tax planning tools available, but it is far from automatic. Eligibility hinges on decisions made at incorporation and sustained throughout the company’s life, not something filed for at the time of sale.
Founders who understand the QSBS holding period requirement and eligibility rules early keep far more control over the outcome than those trying to fix things right before an exit.
QSBS Eligibility Requirements Founders Need to Understand
Eligibility for the qualified small business stock exclusion is tested at both the company level and the shareholder level, and it has to hold up across most of the holding period, not just at issuance.
Company-Level Requirements
The business must be a domestic C-corporation. LLCs, S-corps, and partnerships cannot issue QSBS, which is why founders who started under a different entity structure sometimes miss out entirely. The corporation must also satisfy the applicable gross-asset test when the stock is issued. For stock issued on or before July 4, 2025, the threshold was $50 million. For stock issued after July 4, 2025, the threshold increased to $75 million. At least 80% of company assets must go toward an active qualified trade or business.
Shareholder-Level Requirements
The founder must be an individual, trust, or other non-corporate taxpayer, and the stock must come directly from the company at original issuance, not from a purchase on the secondary market. The QSBS holding period requirement also has to be satisfied before any exclusion can be claimed.
Industries That Don’t Qualify
Some service-based industries are shut out of QSBS entirely, including law, accounting, financial services, healthcare, hospitality, and consulting. Most technology, software, manufacturing, and product-based startups qualify, but it is worth confirming rather than assuming.
How Much Capital Gain Can Founders Exclude With QSBS?
The size of the exclusion depends on when the stock was issued, since the rules changed in 2025.
Stock Issued Before July 4, 2025
For earlier stock, the Section 1202 exclusion allows a founder to exclude the greater of $10 million or 10 times their cost basis, once the stock has been held for more than five years. Since most founders start with very little initial capital, the $10 million figure is usually what applies in practice.
Stock Issued After July 4, 2025
For stock issued after July 4, 2025, the maximum exclusion increased to $15 million, subject to the applicable rules and limitations. The law also introduced a tiered exclusion based on the holding period: 50% after three years, 75% after four years, and 100% after five years. This gives founders planning an earlier exit more flexibility, though holding longer still delivers the strongest outcome.
A Pre-Incorporation and Early-Stage Checklist
Founders who are still early enough to build this in from the start have the most control over the outcome.
Confirm Your Industry Qualifies
Before incorporating, check whether the business falls into an IRS-excluded service category. This one detail decides whether QSBS is even on the table.
Incorporate as a C-Corporation
If a capital gains tax exclusion for startup founders is the goal, the company needs to be a domestic C-corporation from the outset. Converting later resets the holding period clock on any newly issued shares.
File the 83(b) Election on Time
If founder shares are subject to vesting, file an 83(b) election with the IRS within 30 days of issuance. This locks in the tax treatment and starts the holding period clock correctly.
Track Gross Assets at Every Issuance
Keep a running record of the company’s gross assets each time stock is issued. This figure is measured at the moment of issuance and directly affects eligibility.
Structuring the Cap Table Around QSBS
Beyond incorporation, ongoing cap table decisions continue to shape whether QSBS eligibility holds up.
Issue Founder Stock Early
The holding period clock starts at issuance, so issuing shares early, at the lowest reasonable valuation, gives founders a head start toward meeting the required hold.
Watch the Gross Asset Threshold Through Funding Rounds
For VC-funded startups, a large funding round completed right before shares are issued can push the company’s gross assets over the IRS threshold and disqualify that batch of stock. Founders cannot always control round size, but understanding the timing helps avoid an easily preventable mistake.
Document Every Issuance
Cap table records, board consents, and 83(b) filings should build a clear paper trail showing exactly when shares were issued and what the company looked like financially at that moment. That documentation becomes critical years later when eligibility needs to be proven at exit.
Common QSBS Mistakes Founders Make Before a Sale
Even well-intentioned founders lose the qualified small business stock exclusion through avoidable missteps.
Starting as an LLC and Converting Later
Founders who begin as an LLC or S-corp and convert to a C-corporation later often assume their original equity carries the same QSBS treatment. It does not. The holding period only starts on shares issued after the conversion.
Selling or Transferring Shares Too Early
Selling, gifting, or transferring shares before the required holding period is met forfeits the exclusion on those shares entirely, no matter how well the company performs afterward.
Missing Documentation at Exit
Without clear records proving the stock met eligibility requirements at issuance, founders can struggle to substantiate the exclusion exactly when it matters most, during tax due diligence on a sale.
What Happens If You Are Already Past Incorporation
Founders further along are not automatically out of luck.
Reviewing Your Existing Stock
It is worth checking whether the original stock issuance still meets QSBS requirements and whether any later restructuring, funding rounds, or asset growth affected that eligibility.
Structuring Future Issuances
Even if early shares fall short, new stock issued in later rounds can sometimes still be structured to meet QSBS requirements going forward, with the right planning in place.
The Bottom Line
QSBS rewards founders who plan early and document carefully. The structural decisions made at incorporation, when shares are issued, how the cap table is documented, and how the company is structured quietly decide whether millions of dollars in gains are taxable or excluded years down the line. If you are incorporating a new US startup or still early in your cap table decisions, this is worth getting right from the start.