Small Business Taxes in Illinois: LLC vs. S-Corp vs. C-Corp

The tax structure of your Illinois business affects how much you pay to the state and federal government every year. But no single structure is right for every business. The right answer depends on your income level, whether you have employees, your payroll readiness, your CPA costs, and where you expect the business to go in the next few years.

Key Takeaways

•        Illinois income tax is a flat 4.95 percent for individuals. Corporations pay 7 percent on net income plus a 2.5 percent personal property replacement tax.

•        Illinois S corporations pay a 1.5 percent personal property replacement tax on net income. Default LLCs taxed as partnerships also pay 1.5 percent replacement tax.

•        An S corporation election can reduce self-employment tax exposure at higher income levels, but the math depends on your salary level, CPA costs, and payroll obligations.

•        C corporations make sense for businesses planning to raise venture capital, reinvest profits, or offer equity incentives at scale.

•        Illinois LLCs do not have a $500 minimum franchise tax. Consult your CPA for the current tax obligations applicable to your specific entity and income type.

This article explains the mechanics of each structure, what Illinois specifically taxes, and when one structure tends to make more sense than another. It is not a substitute for working with a CPA who knows your specific situation.

If you have not yet formed your LLC:

[LINK: /how-to-start-llc-illinois/ — How to Start an LLC in Illinois: Step-by-Step Guide]

For a full list of business licenses and registrations:

[LINK: /illinois-business-license-permits/ — Illinois Business License and Permits Guide]

Illinois Business Taxes at a Glance

Before comparing structures, understand the Illinois-specific taxes that apply to businesses:

Verify all current rates at the

Illinois Department of Revenue income tax rates page and the IDOR personal property replacement tax page.

How a Default LLC Is Taxed

When you form an LLC without making a tax election, the IRS taxes it based on its structure:

•        Single-member LLC: Treated as a disregarded entity by the IRS. The business income flows to your personal Form 1040, Schedule C. You pay self-employment tax (15.3 percent on the first $168,600 of net earnings for 2024, then 2.9 percent above that — verify the current threshold with the IRS) on top of federal income tax.

•        Multi-member LLC: Treated as a partnership by the IRS by default. Profits and losses flow to each member's personal return via Schedule K-1. Each member generally pays self-employment tax on their share of active income.

Illinois Treatment of Default LLCs

Illinois follows the federal entity classification for most purposes. Single-member LLCs are treated as disregarded entities. Multi-member LLCs treated as partnerships pay the 1.5 percent personal property replacement tax on net income in Illinois.

Members pay Illinois individual income tax at 4.95 percent on their pass-through share of LLC income.

The LLC itself owes the Secretary of State a $75 annual report fee but does not pay the corporate income tax that C corporations pay.

How an S-Corp Is Taxed in Illinois

An S corporation is a tax election, not a separate business entity type. You form an LLC or corporation first, then elect S corporation status with the IRS using Form 2553.

The main tax advantage of an S corporation is that it allows a business owner to split income between a salary (subject to payroll taxes) and distributions (not subject to self-employment tax). At higher income levels, this can produce meaningful savings.

Federal S-Corp Tax Treatment

An S corporation is a pass-through entity at the federal level. Business income passes to shareholders' personal returns via Schedule K-1. Shareholders avoid self-employment tax on the distribution portion. But they must pay themselves a reasonable salary, which is subject to payroll taxes (Social Security and Medicare).

The IRS enforces reasonable compensation rules. Undercompensating yourself to shift income into distributions is an audit risk.

Illinois S-Corp Tax Treatment

Illinois treats S corporations as pass-through entities for income tax purposes. S corporation shareholders pay Illinois individual income tax at 4.95 percent on their share of pass-through income.

Illinois also imposes the personal property replacement tax on S corporations at 1.5 percent of net income. This is lower than the 2.5 percent rate for C corporations.

S corporations with Illinois employees must withhold Illinois income tax at 4.95 percent on employee wages.

When S-Corp Status Might Make Sense

S corporation status tends to make financial sense when:

•        Your LLC net profit is consistently above $50,000 to $80,000 per year (the exact break-even depends on your salary level and payroll costs)

•        You can pay yourself a reasonable salary (typically in the $40,000 to $70,000 range depending on your industry)

•        The payroll tax savings from the distribution portion exceed the cost of running payroll and the additional CPA fees

•        You have a CPA who can manage the additional compliance

The S-corp election does not automatically save money. At lower income levels, the cost of payroll administration and additional accounting can exceed the tax savings. Work through the numbers with a CPA before electing.

How a C-Corp Is Taxed in Illinois

A C corporation is a separate taxable entity. It pays taxes at the corporate level, and shareholders pay taxes again when they receive dividends. This is the double-taxation structure that makes C corporations less attractive for small businesses.

Federal C-Corp Tax Treatment

C corporations pay federal corporate income tax, currently at a flat 21 percent rate. When the corporation distributes profits as dividends to shareholders, those dividends are taxed again at the shareholder level at qualified dividend rates (generally 0, 15, or 20 percent depending on income).

Illinois C-Corp Tax Treatment

C corporations in Illinois pay a 7 percent corporate income tax on net income, per the

Illinois Department of Revenue income tax rates page.

C corporations (and other corporations that are not S corporations) also pay the 2.5 percent personal property replacement tax on net income. See the

IDOR personal property replacement tax page for details.

Combined, the Illinois corporate income tax and replacement tax total 9.5 percent of net income for C corporations, before any federal tax.

When a C-Corp Might Make Sense

C corporations make more sense in specific situations:

•        Venture capital: Most venture capital investors require a Delaware C corporation. Illinois businesses planning VC funding typically form as a Delaware C corp.

•        Reinvesting profits: If profits are reinvested into the business rather than distributed, double taxation is deferred. C corporations can accumulate retained earnings at the 21 percent federal rate before distributions.

•        Equity incentives: Stock options and equity compensation are more straightforward in a C corporation than in an LLC or S corporation.

•        Multi-state growth: C corporations have a cleaner structure for operations that will span many states.

Side-by-Side Tax Comparison

Example Scenarios

The following scenarios are illustrative only. Actual tax outcomes depend on deductions, credits, payroll costs, CPA fees, and federal tax law. Always review your specific situation with a licensed CPA.

Scenario 1: Freelancer Netting $60,000

A freelance designer in Chicago nets $60,000 from their single-member LLC. At $60,000 net profit:

•        Self-employment tax (federal): approximately 14.13 percent after the deduction (approximately $8,478 — verify with IRS tables)

•        Federal income tax: depends on deductions and filing status

•        Illinois individual income tax: 4.95 percent of net income (approximately $2,970)

•        No Illinois replacement tax (disregarded entity)

An S-corp election at $60,000 may or may not save money after accounting for payroll administration costs and additional CPA fees. The break-even is lower at this income level. Run the numbers with a CPA before electing.

Scenario 2: Consultant Netting $120,000

A management consultant in Naperville nets $120,000 from their single-member LLC. At this income level, S-corp election may start to make financial sense, depending on reasonable compensation:

•        With a $60,000 reasonable salary: payroll taxes apply to the $60,000 salary

•        The remaining $60,000 as S-corp distributions avoids self-employment tax

•        Illinois replacement tax at 1.5 percent applies on S-corp net income

•        Payroll administration and CPA fees may run several thousand dollars annually

Whether the savings exceed the costs depends on your specific deductions, CPA rates, and salary level. This illustrates why the calculation is individual.

Scenario 3: Startup Raising Outside Capital

A tech startup in Chicago raising a seed round from institutional investors will almost certainly need to be a Delaware C corporation. The S-corp route is generally incompatible with VC funding because of restrictions on the number and type of shareholders.

Scenario 4: Local Retail Business with Employees

A retail shop in Oak Park with $400,000 in revenue and three employees has payroll tax obligations regardless of entity type. The choice between LLC, S-corp, and C-corp involves evaluating profit margins, owner compensation, and the cost of compliance. A local CPA familiar with Illinois retail and Cook County tax requirements is the right resource.

When an Illinois LLC Might Elect S-Corp Tax Treatment

Consider an S-corp election when:

•        Your LLC is consistently profitable above $50,000 to $80,000 in net income

•        You can pay yourself a defensible reasonable salary without wiping out the payroll tax savings

•        You have or are ready to set up payroll (a payroll service like Gusto or ADP makes this manageable)

•        Your CPA has modeled the specific savings versus costs for your situation

•        You have an accountant who files Form 2553 timely and handles S-corp returns (Form 1120-S)

Do not elect S-corp status based on general advice without running the math on your actual income and costs.

When a C-Corp Might Make Sense

C corporation makes sense when:

•        You are actively seeking venture capital, angel investment, or equity crowdfunding from institutional or accredited investors

•        Your business model requires retaining and reinvesting profits for extended periods without distributing them

•        You plan to offer employee stock options as part of compensation

•        You are building toward an acquisition that will require a clean corporate structure

•        Your CPA and attorney advise it based on your specific growth plans

Registering Your Business with IDOR

Regardless of your structure choice, register with the Illinois Department of Revenue after forming your entity. IDOR handles sales tax, withholding, and other business tax accounts.

IDOR business registration is the starting point.

Your EIN comes from the IRS for free at

IRS EIN application. Do not pay a third party for this.

Talk to a CPA

Tax decisions for a business are not one-size-fits-all. The right structure depends on:

•        Your actual net income and growth projections

•        Your personal tax situation and filing status

•        Your payroll readiness and administrative capacity

•        Retirement plan options (which can vary by structure)

•        The specific Illinois and federal deductions available to you

•        Changes in tax law at the federal level

A licensed CPA with small business experience in Illinois is the right resource before making an S-corp election or setting up a C corporation. The cost of professional advice is almost always less than the cost of getting the structure wrong.

Frequently Asked Questions

Does Illinois have a minimum franchise tax for LLCs?

No. Illinois LLCs do not pay a franchise tax. The $500 minimum franchise tax is a California requirement, not an Illinois one. Illinois LLCs pay a $75 annual report fee to the Secretary of State and are subject to income and replacement taxes through IDOR based on their activities.

What is the Illinois personal property replacement tax?

The personal property replacement tax replaced the former personal property tax in Illinois. It is collected from businesses and distributed to local governments. S corporations and partnerships pay 1.5 percent of net income. C corporations pay 2.5 percent of net income. The rate for S corporations is often overlooked in discussions of S-corp advantages in Illinois.

IDOR personal property replacement tax information

Does an S-corp always save taxes in Illinois?

No. S-corp savings depend on income level, payroll setup, CPA costs, and reasonable compensation requirements. At lower income levels, payroll administration and accounting fees can exceed the self-employment tax savings. At higher income levels and with proper setup, the savings can be meaningful. Model your specific situation with a CPA.

What is the Illinois corporate income tax rate?

Illinois corporations pay a 7 percent income tax on net income. This is in addition to the 2.5 percent personal property replacement tax. The combined rate is 9.5 percent on net income before federal corporate tax. Verify current rates at

IDOR income tax rates page.

How do I register my LLC or corporation for Illinois taxes?

Register through IDOR's MyTax Illinois at

tax.illinois.gov/businesses/registration.html. You will set up the tax accounts that apply to your business, including sales tax if you sell taxable goods, and withholding if you have employees.

Does my Illinois business need to file both federal and state returns?

Yes. Federal and state returns are separate. The entity type determines which forms to file:

•        Single-member LLC (disregarded entity): Schedule C on personal Form 1040 (federal); Illinois Individual Income Tax Return IL-1040

•        Multi-member LLC (partnership): Form 1065 (federal); Illinois Partnership Replacement Tax Return

•        S corporation: Form 1120-S (federal); Illinois S Corporation Replacement Tax Return

•        C corporation: Form 1120 (federal); Illinois Corporation Income and Replacement Tax Return

Your CPA handles the specific state filing requirements for your entity type.

Related Articles