How to choose your business entity in Illinois: LLC, S corp, or C corp, in plain English.

You are about to file paperwork with the Illinois Secretary of State, and it is asking you to choose between three-letter combinations that sound almost the same. LLC, S corp, C corp. Each is a real answer, and each is the wrong answer for a specific set of founders. Here is how to tell which one you are.

The first mistake: treating this as one decision

It is actually two.

Question 1 is a legal decision: what kind of entity do you form with the state? Your only real options in Illinois are LLC (limited liability company), Corporation (Inc.), or, if you have a specific purpose, a Nonprofit Corporation.

Question 2 is a tax decision: how does the IRS treat your entity for federal income tax? Your options are: default (disregarded entity or partnership for LLCs, C corp taxation for corporations), S corp election, or C corp taxation.

Founders who conflate these two think they are choosing between "LLC vs S corp." They are not. LLC is a legal form. S corp is a tax election. An LLC can elect S corp taxation and get most of what founders actually want when they say "S corp."

The default: form an LLC

If you are unsure, form an LLC. Here is why the default is right so often:

• Liability protection is the same. An LLC and a corporation both create a legal wall between your personal assets and the business's obligations, if you keep the entity separate (which is a different post).
• Paperwork is dramatically less. LLCs do not require a board of directors, annual shareholder meetings, or minutes. A single-member LLC files no separate federal return by default; it flows through your personal 1040.
• Illinois annual report is cheap. $75 a year at time of writing.
• You can change the tax election later. An LLC can elect S corp taxation with a single form (Form 2553) once your revenue justifies the payroll overhead.

When the S corp election makes sense

An S corp election lets you pay yourself a "reasonable" W-2 salary as an employee of your own business, and take additional profit as distributions that are not subject to self-employment tax (roughly 15.3% on top of income tax).

That is real money. The catch: you now have to actually run payroll for yourself, file quarterly payroll returns, and defend "reasonable salary" to the IRS if audited.

The rule of thumb: the election starts making sense when your business net income is somewhere between $60,000 and $80,000 a year, depending on how conservative you want to be about salary. Below that, the payroll overhead eats the savings. Above that, the math starts working for you.

Founders often elect S corp too early because a friend or a marketing email said to. The reasonable-salary requirement makes the election meaningfully more expensive to run than a default LLC, and the savings are zero if you would have paid yourself the whole net income as salary anyway.

When a real C corp makes sense

Form a proper C corporation (usually in Delaware, not Illinois) if:

• You plan to raise venture capital. Nearly every US VC will require a Delaware C corp. LLCs are difficult to invest into because their taxes flow through to investors as UBTI, which most institutional LPs cannot accept.
• You plan to issue employee stock options. ISOs require a corporation. LLC "profit interests" exist but are more complicated and less widely understood by employees.
• You want the Qualified Small Business Stock (QSBS) exclusion. Under Section 1202, C corp founders and early shareholders can potentially exclude up to $10 million (or more) of gain from federal tax on a qualifying sale. This is only available for C corps.

C corps come with double taxation (the corp pays tax on income; you pay tax again on dividends) and more paperwork. Both are real costs. The QSBS potential and VC-compatibility are the reasons most tech startups accept them anyway.

Illinois-specific catches

• Illinois franchise tax was repealed in 2024. If you read older guides that mention it, ignore them.
• Illinois LLC annual report is due on the anniversary month. Miss it by 60 days and you are in bad standing; miss it further and you are administratively dissolved. Set a calendar reminder or get someone to set one for you.
• Chicago BACP license is separate from the state filing. Almost every business operating in the city needs at least one. Home-based, retail, food, service - each has a different license and a different fee.
• Cook County has its own rules for some industries. Do not assume Chicago licensing is the whole picture if you are in food service, healthcare, or transportation.

The mistakes we see most often

• Filing an S corp election at formation, based on a Google search. Usually premature; often costs more than it saves.
• Forming in Delaware "because startups do." If you are not raising VC and not issuing options, you now pay registered agent fees in two states for no benefit.
• Using a home address as the registered agent. It is now on the public record forever.
• Skipping the operating agreement for a single-member LLC. Illinois does not require it, but banks, investors, and courts often do. It is what documents that the LLC is a real, separate entity.
• Not registering with the Illinois Department of Revenue. The EIN is federal. State tax registration is a separate step. If you are selling anything taxable in Illinois you also need a use tax registration.

A framework for making the call

1. Are you raising VC or issuing employee options in the next 12 months? → Delaware C corp.
2. Is your realistic net income going to be well below $70K next year? → Illinois LLC, default taxation. Elect S corp later if it starts making sense.
3. Is your net income comfortably above $70K, and are you willing to run payroll on yourself? → Illinois LLC with S corp election.
4. Are you doing this to hold real estate or a passive investment? → Illinois LLC, and talk to an accountant about series LLCs before filing.

None of these are the only correct answer. They are the default answer for the profile they describe. There are legitimate reasons each one might not apply to you.

What we do here at Alpha Momin

We do the discovery call, map your actual revenue and hiring plan onto the tax math, and file the entity that fits. Registered agent, EIN, state tax registration, city licenses, operating agreement, and a compliance calendar all in one engagement. If an S corp election is right for you we make it; if it is a trap we say so, in writing, with the reason.

See the Formation service page for the full scope, timeline, and pricing. When you are ready, the contact form is one click away.

This post is general information, not legal or tax advice. Your specific circumstances may change the answer, which is exactly why we do a discovery call before we file anything.