QSBS Explained: The $15 Million Tax Break Most Founders Don’t Plan For

QSBS (qualified small business stock) is a federal tax break under Section 1202 that lets founders and early investors exclude up to $15 million of gain, or 10 times their basis if that is larger, when they sell stock in a qualifying C corporation. For shares acquired after July 4, 2025, you exclude 50% of the gain after three years, 75% after four and 100% after five. The catch is that most of the rules are decided years before the exit, on the day the stock is issued.

Here is a scene that plays out at a lot of exits. A founder sits at a signing table after six years of work. The acquirer’s lawyers slide over the purchase agreement, the wire numbers are in the deck, and somebody finally asks the question that should have been asked in year one: “Are your shares QSBS?”

Sometimes the answer is yes, and that one sentence is worth millions. Sometimes the answer is “we were an LLC for the first three years,” or “we never filed the 83(b),” or “we bought back a chunk of stock from my co-founder in 2023.” Same company, same exit, completely different tax bill.

QSBS is the biggest tax break most founders never plan for. Not because it is hidden. It sits right there in the tax code. It is ignored because the payoff is five years away and the paperwork happens on day one, when you are busy trying to get your first customer.

This guide is general information, not legal or tax advice. Section 1202 has traps that only a licensed tax attorney or CPA can check against your actual documents. My goal is to make sure you know enough to ask them the right questions early.

What QSBS Actually Is (And Why Congress Just Made It Bigger)

Section 1202 of the Internal Revenue Code has been around since 1993. It was designed to reward people who take the risk of backing small, growing companies. You can read the full text in 26 U.S.C. Section 1202, but here is the plain version.

If you hold qualifying stock long enough and then sell it, part or all of your gain can be excluded from federal income tax. Not deferred. Excluded. On a founder exit that can be the difference between paying roughly 23.8% federal tax on your gain and paying nothing.

The One Big Beautiful Bill Act, signed July 4, 2025, made three big changes for stock acquired after that date:

• Bigger cap: the per-company exclusion rose from $10 million to $15 million per taxpayer (or 10 times basis, whichever is greater), with inflation adjustments starting after 2026.
• Bigger companies qualify: the gross-asset ceiling rose from $50 million to $75 million.
• Faster partial benefit: instead of an all-or-nothing five-year wait, you now get a tiered exclusion starting at three years.

Stock you acquired on or before July 4, 2025 generally stays under the old rules: the $10 million cap and a holding period of more than five years for the 100% exclusion. You cannot simply swap old shares for new ones to reset into the faster schedule.

The New 3, 4 and 5 Year QSBS Holding Periods

This is the part every founder should tape to the wall. For QSBS acquired after July 4, 2025:

*Simplified. The non-excluded part of QSBS gain is taxed at a 28% rate plus the 3.8% net investment income tax where it applies. State tax is separate.

Run the numbers on a simple teaching example. Say you founded a C corp in January 2026, bought your founder shares for almost nothing and sell them for a $12 million gain. Ignoring state tax and assuming every test is met:

Look at that table and then think about every time someone told you to “just get the deal done.” Six months can be worth a million dollars. That does not mean you turn down a great offer to wait for a date on the calendar. It means you know exactly what the calendar is worth before you negotiate.

Who Qualifies: The QSBS Eligibility Checklist

Every one of these has to be true. Miss one and the whole benefit can disappear.

1. The company is a domestic C corporation. Not an S corp. Not a plain LLC taxed as a partnership. It must be a C corp when the stock is issued and during substantially all of the time you hold it.
2. You got the stock at original issue. Directly from the company, for cash, property or services. Shares you buy from another shareholder on a secondary sale generally do not qualify.
3. Gross assets were $75 million or less. At all times before and immediately after your shares were issued ($50 million for stock issued on or before July 4, 2025). This is measured mostly on cash and the tax basis of assets, not your valuation.
4. The company runs an active, qualified business. At least 80% of its assets must be used in a qualified trade or business during substantially all of your holding period.
5. It is not in an excluded field. Health, law, engineering, architecture, accounting, actuarial science, performing arts, consulting, athletics, financial services and brokerage are out, along with businesses whose main asset is the reputation or skill of their people. Banking, insurance, investing, farming, mining and oil extraction, hotels and restaurants are also excluded.
6. You are not a corporation. The exclusion is for individuals and certain trusts and pass-through owners, not corporate shareholders.
7. You held the shares long enough. Three, four or five years under the new tiers.

Software, SaaS, hardware, consumer products, e-commerce and a lot of AI companies usually land on the right side of that list. An agency selling your consulting hours usually does not, even if it is incorporated perfectly.

The Entity Decision You Make on Day One

This is where most founders lose QSBS without ever knowing they had a shot at it.

When you start a company, the default advice for a small, profitable, one-person business is often an LLC or an S corp. I have written about that choice in S corp vs LLC, and for a lot of service businesses that is the right call. Pass-through taxation, simple books, money in your pocket every year.

But if you are building something you plan to sell for eight or nine figures, the math flips. Only C corp stock can be QSBS. If you start as an LLC and convert to a C corp later, the QSBS clock generally starts at conversion, and the value you built before converting is not covered by the exclusion. Three years as an LLC can cost you three years of holding period and all the gain from those years.

Here is the honest trade-off. A C corp pays tax at the corporate level on profits, and dividends are taxed again when they hit you. If you never plan to sell, QSBS is worth nothing and that double tax is real. If you plan to raise venture money and exit, QSBS can be worth more than every annual tax saving combined. Pick the structure for the business you are actually building, and get a licensed advisor to pressure-test it before you file.

Five Ways Founders Accidentally Kill Their QSBS

I would rather you read this list now than hear it from a lawyer at the signing table.

1. Skipping the 83(b) election. If your founder shares vest over time, an 83(b) election filed within 30 days of the grant is usually what starts your holding period on day one instead of each vesting date.
2. Stock buybacks around a funding round. Buying back stock from you or a related person within two years before or after your shares are issued, or significant company-wide buybacks within one year before or after, can disqualify shares. Ask counsel before the company buys anyone out.
3. Sitting on too much cash or investments. If too much of the company sits in idle cash or stock of other companies for too long, the 80% active business test can fail.
4. Drifting into an excluded field. A product company that slowly becomes a consulting firm can lose its qualified status mid-holding period.
5. No paper trail. Keep your stock purchase agreements, board consents, cap table and gross-asset records from the date of issuance. Buyers and auditors will ask for them.

How the $15 Million Cap Really Works

The cap is per taxpayer, per company. You can exclude the greater of $15 million or 10 times your adjusted basis in the stock you sell that year. Most founders bought their shares for a fraction of a cent, so the $15 million figure is the one that matters.

Say your gain on an exit is $40 million and you have held five years. You exclude $15 million, and the other $25 million is taxed at normal long-term capital gains rates. Still a massive win.

Because the cap applies per taxpayer, some families work with estate planners on gifting shares to children or certain non-grantor trusts well before a sale, since QSBS status generally carries over on gifts. That is advanced planning with real rules around it. It is not a do-it-yourself project, and it has to happen long before a term sheet shows up.

There is also a rollover rule, Section 1045, that can let you defer gain if you sell QSBS you held for more than six months and reinvest in new QSBS within 60 days. Useful to know exists. Again, not something to improvise.

How QSBS Fits With Your Cap Table and Exit

QSBS is not just a founder benefit. Your early employees who exercise options and your seed investors may qualify too, which makes your stock more attractive to the right people. When you decide your founder equity split, you are also deciding who has their own $15 million cap on the same exit.

When you finally sell, the structure of the deal matters. A sale of stock is where Section 1202 does its work. An asset sale, where the buyer purchases the company’s assets instead of your shares, can leave you outside the exclusion. Your tax advisor and your M&A attorney should be talking before the letter of intent, not after.

On the tax return itself, the sale goes on Form 8949 and Schedule D, and the excluded amount is reported with code Q. The IRS Form 8949 instructions and IRS Publication 550 walk through the mechanics.

One more thing. Federal QSBS does not mean your state follows along. Some states, California being the best-known, do not conform to Section 1202. Where you live when you sell can change the final number.

What I Would Do If I Were Incorporating Today

1. Decide honestly whether you are building a lifestyle business or something you plan to sell. Only the second one needs QSBS.
2. If it is the second one, talk to a startup attorney about forming a Delaware or home-state C corp from the start.
3. Issue founder shares right away, pay for them with a real check, and file the 83(b) within 30 days if they vest.
4. Track gross assets every time you raise money, and keep records showing you were under the limit at each issuance.
5. Get your CPA to confirm the business is not in an excluded field, and recheck it when your model changes.
6. Avoid buybacks and big cash piles without asking counsel first.
7. Mark your three-, four- and five-year dates on the calendar, and bring them into every acquisition conversation.

The founders who walk away from an exit with the most money are not always the ones with the biggest exit. They are the ones who made a handful of boring decisions correctly in year one. QSBS is one of those decisions. Plan it on day one, and the signing table gets a lot more fun.

QSBS FAQs

What is QSBS in simple terms?

QSBS is qualified small business stock under Section 1202. If you hold original-issue stock in a qualifying C corporation long enough, you can exclude up to $15 million of gain, or 10 times your basis, from federal income tax when you sell.

How long do I need to hold QSBS?

For stock acquired after July 4, 2025, you exclude 50% of gain after three years, 75% after four years and 100% after five years. Stock acquired on or before July 4, 2025 generally needs more than five years for the full exclusion.

Does LLC or S corp stock qualify for QSBS?

No. Only stock issued by a domestic C corporation can qualify. An LLC taxed as a C corp may qualify, and converting later can work, but the holding period generally starts at conversion and earlier growth is not covered.

What is the $75 million gross assets test?

The company’s aggregate gross assets, mostly cash plus the tax basis of other assets, must be $75 million or less before and immediately after your shares are issued. For stock issued on or before July 4, 2025, the limit is $50 million.

Do states follow the QSBS exclusion?

Not all of them. Most states follow federal treatment, but some, with California the best-known example, do not conform to Section 1202. Check your state rules with a licensed CPA or tax attorney before you plan an exit.

This article is general information only and is not legal, tax or financial advice. Section 1202 rules are complex and fact-specific, so speak with a licensed tax attorney or CPA about your situation.