'QSBS Explained: How Founders Can Pay $0 Tax on Gains'

TL;DR: QSBS (qualified small business stock) is a federal tax break under Section 1202 that can let founders and early investors exclude up to 100% of the capital gains when they sell startup stock — up to a per-company cap. To qualify, you generally need stock in a U.S. C-corporation that you got at original issuance and held long enough. The 2025 One Big Beautiful Bill Act made it dramatically more generous: a higher cap ($15 million), a higher company-size limit ($75 million in assets), and a new tiered schedule that starts paying off at three years instead of five.

Last updated: June 2026

What QSBS is

QSBS (qualified small business stock) is stock in a small C-corporation that, if you meet the rules in Internal Revenue Code Section 1202, lets you exclude a large chunk — often all — of your capital gain from federal income tax when you sell.

In plain terms: you build a company, sell your shares years later for a meaningful gain, and a slice (potentially all) of that gain comes out federally tax-free. For founders and early employees, it's one of the largest tax breaks in the code, and most don't realize they're sitting on it.

Two things to know before the details. First, this is a federal break; some states (notably California) don't conform, so your state may still tax the gain. Second, qualifying isn't automatic — it depends on how your company is structured and how you acquired and held the stock.

The core rules: how stock qualifies

For your shares to be QSBS, a set of tests has to be met — some about the company, some about you. The thresholds below reflect the rules as updated for stock acquired or issued after July 4, 2025; stock you got before that date follows the older limits (covered in the next section).

The original-issuance rule is the one founders most often trip on: the stock generally has to come straight from the company (your founder shares, a direct stock purchase, or exercised options), not bought secondhand from someone else's stake.

What the 2025 law (OBBBA) changed

The One Big Beautiful Bill Act, enacted July 4, 2025, expanded Section 1202 in three big ways. The catch: the new rules apply to QSBS acquired (or, for the asset cap, issued) after July 4, 2025. Stock acquired on or before that date keeps the old terms.

1. A new tiered holding period

The old rule was all-or-nothing: hold for five years for the full 100% exclusion, and nothing before that. For stock acquired after July 4, 2025, partial exclusions now kick in earlier:

This is a meaningful change for founders who exit before year five — an earlier acquisition or acquihire no longer means zero QSBS benefit.

2. A higher per-company cap

The exclusion is capped per company. The cap rose from $10 million to $15 million of gain (or 10x your basis, if greater — that alternative is unchanged). For tax years beginning after 2026, the $15M figure will be adjusted annually for inflation.

3. A higher company-size limit

The aggregate gross assets ceiling rose from $50 million to $75 million, also inflation-adjusted after 2026. More companies — and companies that raised more — can now issue QSBS.

Which rules apply to you

If you've held founder stock for years, you're almost certainly on the old (still excellent) 5-year / $10M / $50M track. New grants and new investments ride the expanded rules.

A worked example: what the cap looks like

Suppose you hold founder stock acquired after July 4, 2025, with a basis of $50,000, and you sell five years later for a $20 million gain.

Your per-company exclusion is the greater of $15 million or 10x your basis. Ten times a $50,000 basis is $500,000, so the $15 million figure wins. You exclude $15 million of the gain from federal tax and pay capital gains tax only on the remaining $5 million. At a 5-year hold, the excluded portion is the full 100% allowed under the cap.

Now run the same sale at a four-year hold instead. Under the post–July 2025 tiered schedule, four years gets you a 75% exclusion — so roughly three-quarters of the gain (still subject to the cap) comes out federally tax-free, and the rest is taxed. Wait one more year to cross five years and you reach the full benefit. That single year is often worth structuring the closing around.

A note on stacking: the cap is per taxpayer, per company. Under Section 1202(h), QSBS can be gifted, and the recipient inherits your holding period and basis — so founders sometimes increase total excluded gain across a family by gifting shares to others (such as non-grantor trusts), each with their own cap. It's a real but technical strategy that should only be done with a tax advisor.

Two more rules worth knowing

The excluded gain is also exempt from AMT. For stock that qualifies for the 100% exclusion (generally anything acquired after September 27, 2010), the gain you exclude isn't an alternative minimum tax preference item either — so it doesn't quietly come back as AMT. Treatment of the new partial (50%/75%) tiers is more nuanced; confirm it with your advisor.

Selling before five years? Consider a 1045 rollover. If you have to exit qualifying stock before you hit the holding period, Section 1045 lets you roll the proceeds into other QSBS within 60 days and carry your holding period forward, instead of losing the benefit outright. This is the standard escape hatch in an early acquisition or tender offer.

Common mistakes founders make

• Assuming an LLC qualifies. QSBS requires a C-corporation. Many founders incorporate as an LLC for simplicity and only convert later — which can reset or complicate the holding period. If QSBS matters to you, the entity choice matters from day one.
• Buying stock secondhand. QSBS generally requires original issuance from the company. Acquiring someone else's shares usually doesn't qualify.
• Forgetting the state doesn't follow. A handful of states don't conform to Section 1202, so a "$0 federal tax" exit can still owe meaningful state tax. The usual non-conforming states are California, Alabama, Mississippi, New Jersey, and Pennsylvania (Puerto Rico also doesn't follow it). Check your state.
• Triggering a redemption trap. If your company buys back more than 5% of its stock within a two-year window around issuing QSBS, it can disqualify the stock — an anti-abuse rule meant to stop companies from buying back shares to stay under the asset cap. Loop in your accountant before any buyback near a QSBS issuance.
• Blowing the holding period at exit. Selling a few months shy of a tier (three, four, or five years) can drop you a whole bracket. Time the close if you can.
• No documentation. Years later you'll need to prove the company was QSBS-eligible at issuance — assets under the cap, qualified business, original issuance. Capture it now, not at diligence.

How Afternoon helps

Afternoon keeps the books and entity facts that QSBS eligibility hinges on — gross assets at each issuance, your acquisition dates, and your basis — organized from the start, so the case is already documented when you sell instead of reconstructed under deal pressure.

FAQ

How much tax can QSBS actually save? Potentially all federal capital gains tax on your qualifying gain, up to the per-company cap (now $15M, or 10x basis if greater, for post–July 2025 stock). On a large exit that can be millions in tax excluded.

Do I have to hold the stock for five years? For full (100%) exclusion, yes — but for stock acquired after July 4, 2025, you now get a partial exclusion at three years (50%) and four years (75%). Stock acquired earlier still needs the full five years for any exclusion.

Does my startup qualify as a "qualified small business"? Most software and tech C-corps under the asset cap do. Service fields like health, law, accounting, consulting, finance, and hospitality are excluded. Entity type, asset size, and active business all have to line up.

Is QSBS a federal or state tax break? Federal. Some states conform, some (like California) don't, so you may still owe state tax even when the federal gain is fully excluded.

What if my company started as an LLC? LLCs don't issue QSBS. Converting to a C-corp can start a fresh QSBS clock, but the details matter — get the conversion structured deliberately.

Does the asset cap still apply if my company later raises a huge round? The aggregate gross assets test (now $75M) is measured at and immediately after the stock is issued — not forever. If your company stayed under the cap when your shares were issued, a later round that pushes assets past $75M doesn't retroactively disqualify the stock you already hold. It only affects whether newly issued stock can be QSBS.

Can early employees claim QSBS too, or just founders? Early employees can qualify on the same terms — the rules turn on the stock and how you acquired it, not your title. Shares from exercising options, or a direct stock purchase, can be QSBS if the company and holding-period tests are met.

Related reading

• How to File an 83(b) Election (and the 30-Day Deadline)
• The Cleanest Way to Set Up Your Startup's Legal + Tax Stack (First 90 Days)
• Maximizing Tax Write-offs for VC-backed Startups

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This article is general information, not tax or legal advice. Rules change and your facts matter. Confirm specifics with a qualified professional or talk to Afternoon before you file or register.