Understanding US Business Structures: LLC, S-Corp, and C-Corp for Tax Purposes

Your business structure determines how much tax you pay—and it's one of the few decisions that actually moves the needle on your bottom line. If you're choosing between an LLC, S-Corp, and C-Corp, you're asking a question worth answering carefully.

This guide covers the tax implications of each structure. We'll explain how the IRS taxes sole proprietorships, LLCs, S-Corps, and C-Corps, when each makes sense, and how to shift structures as your business grows.

Sole proprietorship: the default

If you haven't filed anything with your state, you're already operating as a sole proprietorship. It's the IRS's default for anyone working for themselves. You and your business are legally the same thing. All income flows to your personal tax return on Schedule C (Form 1040).

How you're taxed:

Business income is taxed as personal income at your regular tax rate
Self-employment tax of 15.3% applies to your net business income (covering Social Security and Medicare)
No legal separation between your personal assets and business debts

Most freelancers start here. As income grows, the self-employment tax burden—which you pay in full, both employee and employer portions—often motivates a move to a structure where you can split income into salary and distributions.

Limited Liability Company (LLC)

An LLC is a legal structure that separates your personal assets from business liabilities. It's the most popular structure for small-business owners because it offers liability protection without the complexity of a formal corporation.

The tax puzzle: the IRS doesn't have an LLC category

Here's the confusing bit: the IRS doesn't have a specific tax classification for LLCs. Instead, it taxes LLCs based on ownership:

Single-member LLC: Taxed as a sole proprietorship by default. Income goes on Schedule C. You pay income tax and self-employment tax on net profit, just like a solo proprietor.

Multi-member LLC: Taxed as a partnership by default. The LLC files Form 1065 (informational only), each owner gets a Schedule K-1, and each owner pays income and self-employment tax on their share.

The hidden power: you can choose your tax treatment

The real advantage of an LLC is flexibility. You can change how the IRS taxes your LLC without changing the legal structure by filing a single form. Your LLC can elect to be taxed as an S-Corp or C-Corp instead. This is done with:

Form 2553 — to elect S-Corp taxation
Form 8832 — to elect C-Corp taxation

You keep the liability protection and legal simplicity of the LLC while choosing the tax treatment that fits your business best.

S-Corporation (S-Corp)

An S-Corp isn't a separate legal entity—it's a tax election. Both actual corporations and LLCs can elect S-Corp taxation. The "S" refers to Subchapter S of the tax code.

How S-Corp taxation works

An S-Corp is a pass-through entity. Income passes to the owners' personal tax returns and is taxed at individual rates. The S-Corp itself pays no federal income tax.

The tax advantage comes from splitting your income into two parts.

Salary: As an S-Corp owner-employee, you must pay yourself a "reasonable salary" for the work you actually do. This salary is subject to payroll tax—15.3% total for Social Security and Medicare, split between employer and employee.

Distributions: Any profit left after your salary can be taken as distributions. Distributions are taxed as income to you, but they skip the 15.3% payroll tax entirely.

A real example

Say your business generates $150,000 in net profit.

Operating as a sole proprietorship:

Self-employment tax on $150,000 = roughly $21,200
Plus income tax on the full $150,000

Operating as an S-Corp with an $80,000 salary:

Payroll tax on $80,000 salary = roughly $12,200
Distributions of $70,000 = zero payroll tax
Income tax on the full $150,000

Tax savings: Approximately $9,000 in payroll taxes alone—and that's before accounting for any difference in marginal tax rates.

This is why profitable small businesses often elect S-Corp status. The savings usually exceed the added administrative cost.

S-Corp requirements

S-Corps come with restrictions:

Up to 100 shareholders — all must be US citizens or residents
One class of stock — all shares must have equal rights and voting power
Calendar year — you must use January–December (with rare exceptions)
Reasonable salary rule — the IRS watches for owners paying themselves too little to dodge payroll tax. Get this wrong, and the IRS reclassifies distributions as wages and assesses penalties.
Payroll administration — you must actually run payroll, withhold taxes, file returns
State considerations — some states don't recognize S-Corp elections or impose additional taxes on S-Corps

When S-Corp makes sense

The rule of thumb: S-Corp election usually pencils out when net business income hits $50,000–$60,000 per year. Below that, the cost and complexity of running payroll outweigh the tax savings. You need enough distributions to justify the administrative burden.

If you're self-employed as a consultant, contractor, or freelancer, an S-Corp can be particularly attractive because your profit margin is often substantial relative to the salary you need to pay yourself.

C-Corporation (C-Corp)

A C-Corp is taxed under Subchapter C. Unlike pass-through entities, a C-Corp is a separate taxpaying entity. The corporation pays tax. Then you pay tax again when you take money out.

Double taxation: it's as real as it sounds

Corporate tax: The corporation pays a flat 21% federal income tax on its profits
Shareholder tax: When profits are distributed to shareholders as dividends, shareholders pay tax again at their individual rate (qualified dividends get preferential treatment at 0%, 15%, or 20%, but they're still taxed)

This is double taxation, and it's why most small-business owners avoid C-Corps.

When C-Corp actually works in your favour

Despite double taxation, C-Corps are the right choice in specific situations:

You're reinvesting profits. If your business retains most earnings for growth rather than distributing them, the 21% flat corporate tax rate might be lower than your personal rate (which can reach 37% for high earners). The tax defers until you eventually take the money out.

Raising venture capital. If institutional investors are involved, they typically require C-Corp structure.

Employee incentives. C-Corps can offer incentive stock options (ISOs) and qualified small business stock (QSBS) benefits—valuable for recruiting and motivating employees.

Unlimited shareholders. No cap on number or type of shareholders, and you can have foreign owners.

Multiple stock classes. Preferred stock, common stock, and other classes—useful for investor rounds and founder/employee alignment.

Qualified Small Business Stock (QSBS). Under Section 1202, if you hold C-Corp stock for five+ years, you may exclude up to $10 million in capital gains from federal tax when you eventually sell. For founders, this can mean tens of millions in tax-free gains.

Comparing your options

Factor	Sole Prop/LLC	S-Corp	C-Corp
Does entity pay tax?	No	No	Yes (21%)
Income passes to owners?	Yes	Yes	No
Self-employment tax	On all profit	On salary only	No (payroll only)
Payroll required?	No	Yes	Yes
Shareholder limits	None	100 US individuals	None
Stock classes	N/A	One class	Unlimited
Complexity	Low	Medium	High
Best for	Starting out, low income	$50K+ profitable businesses	Funded startups, high growth

Making your choice

Start with these questions:

What's your profit level? Higher income favours S-Corp because the payroll tax savings compound. Below $50K, the admin cost usually outweighs the benefit.
Are you raising investment? Venture capital requires a C-Corp. Bootstrapping? LLC or S-Corp is simpler.
How many owners? More than 100 shareholders, foreign owners, or employee equity? You need a C-Corp. Otherwise, an LLC or S-Corp is usually simpler.
State rules matter. Some states tax S-Corps or C-Corps differently. Check your state's rules before deciding.
How much paperwork tolerance? Payroll, estimated taxes, more forms. S-Corps and C-Corps require more admin. If that feels painful, start simple.

The cheapest option isn't always the best. The best option is the one that saves you the most money after accounting for your own time and complexity.

Frequently Asked Questions

Can I switch structures later? Yes. You can transition from sole proprietor to LLC (state filing only), LLC to S-Corp (Form 2553), S-Corp to C-Corp, or back again. Timing matters because some transitions have tax consequences—particularly built-in gains tax when switching from S-Corp to C-Corp. Work with a tax professional before switching.

If I elect S-Corp taxation, does my LLC become a corporation? No. Your LLC remains an LLC legally. Only the tax treatment changes. You keep the liability protection and legal simplicity of the LLC while filing S-Corp tax forms with the IRS. This is why many small businesses use an LLC taxed as an S-Corp—it gives you the best of both.

Do I need an S-Corp if I'm a solo freelancer? Not necessarily. If your net profit is under $60,000, the payroll administration cost and complexity usually outweigh the tax savings. If you're consistently clearing $80,000–$100,000+, an S-Corp often makes sense. A tax professional can run the numbers for your specific situation.

What does "reasonable salary" actually mean for S-Corp owners? It's whatever you'd legitimately pay someone else to do your job. If your web design business clears $120,000 profit, taking a $40,000 salary and $80,000 distributions might be defensible. Taking a $10,000 salary to minimize payroll tax? The IRS will challenge it. "Reasonable" is fact-specific and depends on your industry, experience, and role. A CPA or tax attorney can help you set a defensible number.

Does state tax affect this decision? Yes, substantially. Some states don't recognize S-Corp elections. Others impose franchise taxes on C-Corps or S-Corps. Some tax LLCs differently than the IRS. Your federal structure doesn't always align with your state's treatment. This is a key reason to consult with a tax professional who knows your state's rules.

What about self-employed health insurance deductions? Sole proprietors and LLC owners (taxed as sole proprietors or partnerships) can deduct self-employed health insurance premiums. S-Corp and C-Corp owners are treated as employees and get a different deduction mechanism. It's a small difference but worth knowing when comparing structures.

If I elect S-Corp and later regret it, can I switch back? Yes, but the IRS imposes a five-year waiting period. Once you revoke S-Corp election, you can't re-elect for five years without IRS permission. Don't make this election lightly.

When should I actually talk to a tax professional? Now. Before you choose a structure. This is one of the few business decisions where professional advice pays for itself immediately. The cost of a consultation is trivial compared to operating under the wrong structure for a year or two.

Building the foundation: records

Whatever structure you choose, everything depends on accurate records. Your accounting system needs to track income and expenses with enough detail to support your tax return—and to show the IRS exactly how your chosen structure was applied.

If you're an S-Corp, you need clear salary vs. distribution data. If you're a C-Corp, retained earnings must be tracked separately. If you're a sole proprietor, Schedule C documentation needs to be crisp.

Use a business bank account from day one—separate personal and business transactions. Then record every transaction as it happens. By year-end, your tax prep becomes substantially simpler because the hard work is already done.

Relentify's accounting platform helps US-based small businesses track income, expenses, and owner distributions with the detail your tax return requires. Build the habit of recording transactions as they happen, and you'll have accurate records that make tax time faster and less stressful.