S Corp vs. C Corp: The Differences That Matter When Advising a Client

9/25/2026

Clients ask "S corp or C corp?" as if it were a question about paperwork. It is really a question about where the income gets taxed, how many times, and what happens when the owner wants the money out, including at the exit years from now. Both are corporations under state law. The difference is federal tax status: a C corporation is a separate taxpayer that files Form 1120 and pays its own income tax, while an S corporation has elected under Subchapter S to pass its income, deductions and credits through to shareholders, who report them on their own returns from a Schedule K-1 to Form 1120-S.

That one difference drives everything else in this comparison. This page works through it the way a practitioner needs to: the mechanics of each system, the eligibility limits that take S status off the table for some clients, the current corporate rate and the qualified small business stock rules as amended in 2025, and the situations where a C corporation is genuinely the better answer rather than an accident of history.

The Core Difference: One Level of Tax or Two

A C corporation pays tax on its own taxable income. The federal rate is a flat 21%. The Tax Cuts and Jobs Act set that rate permanently, and the One Big Beautiful Bill Act (P.L. 119-21, July 2025) left it in place. When the corporation later distributes after-tax earnings as dividends, the shareholders pay tax again. Qualified dividends are taxed at the long-term capital gains rates (0%, 15% or 20%), and higher-income shareholders may also owe the 3.8% net investment income tax. That second layer is what people mean by the "C corp double tax."

An S corporation generally pays no federal income tax at the entity level. Its income flows through to shareholders in proportion to their stock ownership, whether or not it is distributed, and is taxed at their individual rates. Distributions of income that has already been taxed generally come out without a second tax, to the extent of the shareholder's stock basis. There are exceptions at the entity level, covered below, but the default is one layer of tax.

A worked comparison of the C corp double tax

Take a business with $500,000 of taxable income in a year, owned by a single individual in the top brackets, and assume every dollar left after tax is paid out.

Step	C corporation	S corporation
Entity-level federal tax	$105,000 (21%)	Generally none
Amount available to the owner	$395,000 dividend	$500,000 of flow-through income
Owner-level tax on that amount	$94,010 (20% + 3.8% NIIT on the dividend)	Ordinary rates up to 37%, possibly reduced by the Section 199A deduction
Combined federal rate (approx.)	39.8%	Depends on the owner's bracket, QBI eligibility and wage mix

The C corporation's combined rate on fully distributed earnings, 21% plus 23.8% on the remaining 79%, works out to roughly 39.8%. That number is the right starting point for a client conversation, but it is a starting point only. It ignores state taxes at both levels, it assumes everything is distributed now, and it ignores that an S corporation shareholder who works in the business takes part of the income as wages subject to employment taxes. Run the actual numbers for the actual client.

Why the "double tax" is often smaller in practice

The second layer only bites when earnings come out as dividends. Owner-employees of closely held C corporations have traditionally reduced it by:

Paying reasonable compensation, which the corporation deducts. Salary is taxed once, at the individual level, plus employment taxes. Compensation must be reasonable; excessive pay to a shareholder can be recharacterized as a nondeductible dividend.
Retaining earnings to fund growth, so the only current tax is the 21% entity tax.
Holding the stock until death, when heirs may take a stepped-up basis.
Selling the stock rather than distributing earnings, so the shareholder recognizes capital gain, which may be excluded entirely if the stock is qualified small business stock (see below).

Each of these has limits. Retained earnings beyond the reasonable needs of the business can trigger the accumulated earnings tax, and a closely held corporation earning mostly passive income can fall into the personal holding company rules. Both are penalty taxes designed to stop a corporation from being used as an indefinite tax shelter at the corporate rate.

The S Corporation's Entity-Level Exceptions

"Pass-through" is the rule, not an absolute. An adviser comparing the two needs to know where an S corporation can still owe tax itself:

Built-in gains tax (Section 1374). A C corporation that converts to S status, or an S corporation that acquires assets from a C corporation in a carryover-basis transaction, can owe corporate-level tax on gain that was built in at the conversion date if the assets are sold within the five-year recognition period.
Excess passive investment income (Section 1375). An S corporation that has accumulated earnings and profits from C corporation years and earns passive investment income above 25% of gross receipts can owe an entity-level tax. If that condition continues for three consecutive years, the S election terminates.
LIFO recapture when a C corporation using LIFO converts to S status.
State taxes. Many states tax S corporations at the entity level in some form, and a few do not recognize the federal election at all. New York City is the classic example: it does not recognize the S election, so S corporations doing business there are subject to the city's general corporation tax.

The C-to-S conversion items matter most when the client's question is not "which should we form?" but "should our existing C corporation elect S status?" That is a different analysis, and the built-in gains exposure often decides it.

Eligibility: Why S Status Is Not Always Available

A C corporation can have any shareholders, any number of them, and any capital structure. An S corporation cannot. Under Section 1361 and the Form 2553 instructions, a corporation can elect S status only if it:

Is a domestic corporation, or a domestic entity eligible to elect corporate treatment (an LLC, for example).
Has no more than 100 shareholders, with spouses and members of a family able to be counted as one shareholder.
Has only eligible shareholders: individuals, estates, certain trusts, and certain exempt organizations. Partnerships, C corporations and most LLCs taxed as partnerships cannot hold S stock directly.
Has no nonresident alien shareholders.
Has only one class of stock. Differences in voting rights are allowed; differences in distribution or liquidation rights are not.
Is not an ineligible corporation, such as certain banks and insurance companies.

These are not paperwork details. A client who wants to bring in a venture fund, issue preferred stock to an angel investor, grant a foreign co-founder equity, or have another company own part of the business is describing a C corporation (or a partnership), not an S corporation. Breaking any of these rules after the election terminates it, and the corporation generally cannot re-elect for five years without IRS consent.

Compensation, Payroll and Employment Taxes

Both entity types pay owner-employees through payroll. The differences are in what the rest of the income does.

In an S corporation, the shareholder-employee's wages are subject to FICA and income tax withholding, and the remaining flow-through income is generally not subject to self-employment or FICA taxes. That is the main reason single-owner service businesses elect S status, and it is also why the IRS focuses on whether wages are reasonable. Our post on payroll for an S corp election covers how to set and document reasonable compensation before the first payroll runs.

In a C corporation, there is no comparable "wage versus distribution" game. Wages are deductible and taxed once, plus FICA. Dividends are not deductible and are taxed twice, but carry no FICA. The planning question is the balance between deductible compensation and double-taxed dividends, constrained by what is reasonable for the services performed.

Fringe benefits treat the two differently. A C corporation can generally provide owner-employees the same tax-favored benefits it gives other employees. In an S corporation, a more-than-2% shareholder is treated like a partner for many fringe benefits: employer-paid health insurance premiums, for example, are included in the shareholder's W-2 wages and deducted (if allowed) at the individual level rather than excluded. For clients who reimburse expenses, an accountable plan works in either structure and is worth setting up early.

The Qualified Business Income Deduction

S corporation shareholders may be eligible for the Section 199A deduction of up to 20% of qualified business income. The OBBBA made the deduction permanent, kept the 20% rate, and added a minimum deduction for taxpayers with at least a modest amount of QBI from active businesses, for tax years beginning after 2025. Wages paid to the shareholder are not QBI, and for owners above the income thresholds the deduction can be limited by the W-2 wages the business pays and the type of business. A C corporation has no 199A deduction; its income is taxed at 21% instead.

That interaction is why "pass-through is always cheaper" is wrong. An owner in the top bracket whose business does not qualify for the full QBI deduction pays up to 37% on S corporation income every year, whether or not it is distributed. The same owner could pay 21% inside a C corporation on earnings that are reinvested. Which result is better depends on how much will be distributed, when, and how the owner intends to exit.

Qualified Small Business Stock: Section 1202 After 2025

Section 1202 is often the single largest factor in favor of C status for a growth company, and it was expanded in 2025. Only stock of a C corporation can be qualified small business stock; stock issued while the company is an S corporation never qualifies, although stock issued after a conversion to C status can.

For QSBS issued after July 4, 2025, the OBBBA:

Introduced a tiered holding period: a 50% gain exclusion after three years, 75% after four years, and 100% after five years.
Raised the per-issuer exclusion cap from $10 million to $15 million (or 10 times the shareholder's basis, if greater), with inflation indexing in later years.
Raised the corporation's aggregate gross asset limit from $50 million to $75 million, also indexed in later years.

Stock issued on or before July 4, 2025 stays under the prior rules, including the five-year holding requirement for any exclusion. The other requirements did not go away: the stock must be acquired at original issuance, the corporation must meet the active business requirement, and many service fields (health, law, accounting, consulting, financial services and others) are excluded. A company that expects to be sold at a large gain, raise outside capital and reinvest earnings is the profile where QSBS can make the C corporation the clearly better choice.

Losses, Basis and the Early Years

S corporation losses flow through to shareholders, subject to their stock and debt basis, the at-risk rules and the passive activity rules. A shareholder gets debt basis only for loans they personally make to the corporation, not for bank debt the corporation borrows, even if the shareholder guarantees it.

C corporation losses stay inside the corporation as net operating losses that offset future corporate income. They do not help the owner's personal return.

A start-up that expects real losses in its first years, funded by owners with other income, often prefers flow-through treatment for that reason. (If those losses will be funded with entity-level debt, partnership taxation usually handles basis better than S status; the hub comparison of S corporations, partnerships and LLCs covers that point.)

Exit and Sale Considerations

Entity choice is usually made for the first year and lived with for twenty. The exit is where a wrong choice gets expensive.

Asset sales. A C corporation selling its assets pays corporate tax on the gain, and the shareholders pay again when the proceeds are distributed. An S corporation's asset sale gain generally flows through once (subject to built-in gains tax for converted C corporations).
Stock sales. Buyers often prefer asset purchases for the basis step-up. With an S corporation, a stock sale can sometimes be treated as an asset purchase through elections under Section 338(h)(10) or 336(e), which is harder to achieve with a C corporation without the double-tax cost.
For a C corporation whose stock qualifies, a stock sale can be partly or fully excluded from the seller's income, which can outweigh everything above.

Due diligence work at exit, including quality-of-earnings analysis, is covered in our post on financial statement analysis for M&A due diligence.

When C Status Actually Wins

Advisers default to S status for small, profitable, owner-operated businesses, usually correctly. C status tends to win when one or more of these is true:

The client needs investors S status cannot accommodate: venture funds, corporate investors, foreign owners, or more than 100 shareholders.
The capital structure needs more than one class of stock, such as preferred stock with a liquidation preference.
The company will reinvest most earnings for years, so the owner benefits from the 21% rate on retained income rather than paying individual rates on income they never receive.
QSBS is realistic: an eligible business, original-issue stock, a five-year horizon and a plausible large exit.
The owner wants full tax-favored fringe benefits as an employee.
The owner's individual rate is high and the QBI deduction is limited or unavailable, which narrows the pass-through advantage.

S status tends to win when the business distributes most of its profit, has a small number of individual owners, expects early losses that the owners can use, or will eventually be sold in an asset sale.

How to Frame It for the Client

The most useful framing is a three-question checklist:

Who will own it? If the answer includes anyone ineligible, the S question is over.
Where will the money go? Mostly to the owners each year, or mostly back into the business?
How does this end? A sale of assets, a sale of stock, a transfer to family, or a slow wind-down?

Then model both structures with the client's actual figures, including state taxes, payroll costs and the QBI deduction. A choice made from a rule of thumb usually fails at the third question.

Building the Skill

S corporation work runs through elections, basis, distributions, shareholder compensation and the built-in gains rules, and most of it is learned on live engagements where mistakes are expensive. Our S Corporations course covers the S corporation side of this comparison, and practitioners who handle S corporation transactions regularly can go further with the Certificate in S Corp Transactions. For definitions of the terms used here, the glossary of accounting terms and our tax prep FAQs are useful companions.

Frequently Asked Questions

What is the main difference between an S corp and a C corp?

Tax status. Both are corporations under state law, but a C corporation pays federal income tax on its own profits at 21% and its shareholders pay tax again on dividends. An S corporation has elected to pass its income through to shareholders, who report it on their own returns whether or not it is distributed, so there is generally only one level of federal tax. S status also comes with eligibility limits: no more than 100 shareholders, only eligible shareholder types, no nonresident aliens, and one class of stock.

How does the C corp double tax work?

The corporation pays 21% federal tax on its taxable income. When it distributes what is left as a dividend, the shareholder pays tax on the dividend, at up to 20% for qualified dividends plus the 3.8% net investment income tax for higher-income taxpayers. On fully distributed earnings for a top-bracket shareholder, the combined federal rate is roughly 39.8%. Paying reasonable salaries, retaining earnings for growth, and selling stock rather than distributing earnings can reduce the second layer in practice.

Is the 21% corporate tax rate permanent?

Yes. The Tax Cuts and Jobs Act set a flat 21% corporate rate without a sunset date, and the One Big Beautiful Bill Act in July 2025 did not change it. Congress can always amend the rate in future legislation, but under current law it is not scheduled to change. State corporate income taxes are separate and vary widely, so the total rate a C corporation pays depends on where it does business.

Can an S corporation have qualified small business stock?

No. Section 1202 requires the stock to be issued by a C corporation, and stock issued while a company is an S corporation never qualifies, even if the company later converts. Stock issued after a conversion to C status can qualify if all the other requirements are met. For stock issued after July 4, 2025, the exclusion is tiered at 50%, 75% and 100% for three, four and five years of holding, with a $15 million per-issuer cap.

When should a client choose a C corp over an S corp?

When the owners or capital structure do not fit the S rules (outside investors, foreign owners, preferred stock), when most earnings will be reinvested for years, when a large exit makes the QSBS exclusion realistic, or when the owner's individual rate is high and the QBI deduction is limited. For a small, profitable business whose owners take most of the profit each year, S status usually produces less total tax. The decision should be modeled with the client's own numbers, including state taxes.

Can a C corporation convert to an S corporation later?

Yes, if it meets the eligibility requirements, by filing Form 2553 with consent from all shareholders. The conversion has consequences: assets with built-in gain at the conversion date can trigger a corporate-level built-in gains tax if sold within five years, LIFO inventory can trigger recapture, and accumulated earnings from C years can create passive investment income problems. Model those costs before recommending the election for an existing C corporation.