S-Corp vs C-Corp When Selling Your Business: Complete Tax Guide

Entity structure is the most overlooked pre-sale tax variable — and one of the most impactful. On a $10M sale, the difference between an S-corp, a C-corp without QSBS, and a C-corp with QSBS can exceed $3M in after-tax proceeds. This guide explains why, and how to think about your situation.

How S-corp sellers are taxed

S-corporations are pass-through entities — the corporation pays no federal income tax on a sale. Gain flows directly to the shareholders and is taxed once, at the individual level. For most owners who have held the business long-term, that means long-term capital gains rates: 20% federal plus 3.8% Net Investment Income Tax for high earners, for a combined 23.8% on income above the threshold ($613,700 MFJ / $576,450 single in 2026).²

In a stock sale, the entire proceeds produce capital gain — favorable rates, no complications. Asset sales produce a blended rate because equipment depreciation recapture is taxed at ordinary rates (up to 37%), covenants not to compete are ordinary income, and only goodwill and appreciated real estate are truly LTCG. Most S-corp sellers prefer stock sales for this reason.

The §338(h)(10) election: S-corp's hidden negotiating tool

When a buyer acquires 80%+ of an S-corp's stock in a single purchase, both parties can jointly elect §338(h)(10), which treats the deal as a deemed asset purchase for federal tax purposes — while leaving it a legal stock sale.³

Why buyers want it: Asset purchase treatment gives the buyer a stepped-up basis in all the business's assets. That step-up gets depreciated and amortized, producing future tax deductions worth — in present value — roughly 20–30% of the purchase price for a capital-intensive or IP-heavy business. Without the step-up, the buyer inherits the seller's low-basis assets and gets far fewer future deductions.

What it means for sellers: The deemed asset sale can produce more ordinary income than a pure stock sale (same recapture issue as a cash asset sale). On a goodwill-heavy business, the difference is small. On a business with significant equipment, inventory, or §1245 recapture, the seller's tax bill rises.

The negotiating implication: A buyer who wants §338(h)(10) treatment should pay a higher price to compensate the seller for the extra tax. The spread — the "structure premium" — is typically $0.50–$1.50 for every $1.00 of buyer tax benefit. If a buyer is asking for §338(h)(10) without offering a premium, they're asking for a $0 concession worth potentially hundreds of thousands to them.

See our full asset sale vs stock sale guide for the allocation mechanics and negotiating framework.

How C-corp sellers are taxed — the double-tax problem

C-corporations pay federal income tax at the entity level — 21% on net income, including gains from a sale.⁴ When the after-tax proceeds are distributed to shareholders as a liquidating distribution, shareholders recognize gain on their stock — taxed at capital gains rates (up to 23.8%).

The result is two layers of tax on the same economic gain.

This is why most business owners structure as S-corps, LLCs, or partnerships — to avoid the double tax. A C-corp structure only makes sense for a business sale if QSBS applies, or if the business has never been profitable enough to distribute (the "accumulated deficit" offset). For most mid-market founders, the C-corp double tax is a $1.5M–$4M penalty relative to pass-through structure.

When C-corp wins: QSBS §1202

Section 1202 of the Internal Revenue Code allows shareholders of qualified small business stock (QSBS) to exclude 100% of capital gains on a sale — up to $15M per issuer per taxpayer, permanently under the One Big Beautiful Bill Act (OBBBA) signed July 2025.¹

The QSBS exclusion turns the C-corp's double-tax problem entirely upside down. A $10M sale with QSBS pays zero federal capital gains tax — compared to $2.38M for an S-corp seller and $3.98M for a C-corp without QSBS.

QSBS requirements

To qualify, five conditions must all be met at the time of sale:

1. C-corp at original issuance: The stock must have been issued by a domestic C-corporation. S-corp stock does not qualify.⁵
2. 5-year holding period: The shareholder must have held the stock for more than 5 years continuously.
3. Active business: At least 80% of assets must be used in active business (professional services fields including law, health, financial services are excluded from QSBS).
4. Gross assets ≤$50M: The corporation's gross assets must have been $50M or less at original issuance and immediately after.
5. Original acquisition: The shareholder must have acquired the stock at original issuance (not on secondary market), in exchange for money, services, or property.

The $15M cap is per issuer per taxpayer. A married couple each holding stock in their own names doubles the exclusion to $30M. Stacking across multiple non-grantor trusts can extend it further — see our QSBS stacking guide for the mechanics.

The built-in gains (BIG) tax trap

Here's a scenario that catches business owners off guard: You operated as a C-corp, then elected S-corp status to get pass-through treatment — and now you're selling within 5 years of that election.

IRC §1374 imposes a built-in gains tax on S-corporations that were formerly C-corporations.⁶ During the 5-year recognition period following the S-election, any gain on assets that were appreciated at the time of conversion is taxed at the C-corp rate (21%) at the entity level — even though the company is now an S-corp. That gain then also flows through to shareholders and is taxed again at their individual rates.

The result: If your $10M business was valued at $3M when you elected S status 3 years ago, the $3M of pre-conversion appreciation is subject to BIG tax (21% = $630K) on top of the normal pass-through tax. You get pass-through treatment only on appreciation that accrued after the S-election.

If you have a pending sale and elected S-corp status fewer than 5 years ago, model the BIG tax before assuming you're getting pass-through treatment on the full gain. The 5-year recognition period runs from the first day of the first taxable year as an S-corp.

Can you convert S-corp to C-corp to unlock QSBS?

This is one of the most common questions exit-planning advisors hear from owners with 5–10 years before a planned sale. The logic is appealing: convert the S-corp to a C-corp now, let the 5-year QSBS clock run, and sell tax-free.

The mechanics: An S-corp can revoke its S-election (or restructure via an F-reorganization under §368(a)(1)(F)), which converts it to a C-corp without triggering immediate tax. There is no "S-to-C built-in gains" equivalent — the BIG tax only applies to C→S conversions, not S→C.

The QSBS eligibility question: Here's the complication. §1202 requires that stock be originally issued by a C-corporation. Whether existing S-corp shares that survive an F-reorganization become "QSBS-eligible" is a nuanced legal question — the IRS has issued some favorable private letter rulings, but the analysis depends heavily on how the conversion is structured. A clean F-reorg generally gives the best argument for QSBS eligibility starting from the conversion date, but it is not settled doctrine.

Practical guidance:

• If you're 5+ years from exit and your business is under $50M in gross assets, a conversion to C-corp may be worth analyzing. The QSBS math is compelling enough to justify the complexity — get a tax attorney's written opinion on QSBS eligibility before committing.
• If you're 2–4 years out, the window is tight. Even if QSBS eligibility is clean, you need 5 years of holding period. Conversion now means QSBS benefit only if the sale slips past year 5.
• If you're selling within 2 years, conversion doesn't help. Focus instead on §338(h)(10) negotiations, installment sale structures, CRT pre-sale planning, or estate strategies. See our exit planning timeline for what's still on the table.

One more consideration: Converting to a C-corp eliminates future pass-through distributions. If the business continues to generate income for several years post-conversion (before sale), those earnings are subject to C-corp double tax on distribution. The QSBS benefit at exit must be weighed against interim distribution tax cost.

Decision framework: which structure wins for you?

The role of an exit-planning advisor

Entity structure decisions interact with QSBS stacking, installment sale mechanics, estate planning, and deal structure in ways that are hard to model without seeing the full picture. An investment banker won't touch this — it's not their job. An M&A attorney will flag the issues but won't run the financial plan. A CPA typically models the current structure, not the optimal one.

A fee-only financial advisor who specializes in business exits looks at the full stack: what structure you're in today, what changes are still available given your timeline, how each option interacts with your estate plan, and what the after-tax number actually looks like across scenarios. The right answer for a founder with a $25M business and 7 years before exit is completely different from the answer for someone with an LOI on the table in 60 days.

Related guides: QSBS Section 1202 complete guide · Asset sale vs stock sale: the tax math · ESOP exit: Section 1042 deferral · Exit planning timeline

Sources

1. One Big Beautiful Bill Act (OBBBA), Pub. L. 119-XX, signed July 4, 2025 — IRC §1202 QSBS exclusion cap permanently raised to $15,000,000 per taxpayer per issuer; tiered exclusion rates (50/75/100%) for stock held 3/4/5+ years preserved; 5-year holding period requirement unchanged.
2. IRS Revenue Procedure 2025-67 — 2026 inflation-adjusted tax parameters. LTCG rate of 20% applies at taxable income above $613,700 MFJ / $576,450 single. Net Investment Income Tax (NIIT) of 3.8% under IRC §1411 applies at MAGI above $250,000 MFJ / $200,000 single (not inflation-adjusted).
3. Treas. Reg. §1.338(h)(10)-1(c) — §338(h)(10) election availability for S-corp targets. Requires qualified stock purchase (80%+), joint election by buyer and all S-corp shareholders, Form 8023 filed by 9th month after acquisition.
4. IRC §11(b) — C-corporation tax rate of 21% on all taxable income, as permanently set by the Tax Cuts and Jobs Act of 2017.
5. IRC §1202(c)(1) — Qualified small business stock must be stock in a domestic C-corporation; §1202(e)(3) lists excluded industries (health, law, financial services, etc.); §1202(b)(1) sets aggregate gain exclusion at $10M or 10× basis (OBBBA raised this to $15M).
6. IRC §1374 — Built-in gains tax. Applies to S-corporations that were formerly C-corporations. Recognition period: 5 taxable years beginning with first day of first S-corp tax year (permanently set at 5 years for tax years beginning on or after January 1, 2015, per TCJA §13543). BIG tax rate: highest rate under IRC §11(b), currently 21%.

Tax values in this guide reflect 2026 law including OBBBA (July 2025) and TCJA permanent provisions. This page does not constitute financial, tax, or legal advice. QSBS eligibility following an S-to-C conversion is a complex area; obtain written legal opinion before relying on §1202 exclusion in a conversion context.