Illinois LLC vs Corporation: Formation Steps, Fees and Tax Differences

The Illinois LLC vs corporation decision turns on three practical questions: how much paperwork you want after formation, how the entity is taxed in Illinois and federally, and who your owners are. Both entities limit personal liability when you respect the formalities, and both cost the same $150 to form with the Secretary of State. The differences show up later, in franchise tax for corporations, replacement tax rates, who may own an S corporation, and how much governance the law expects you to document.

Illinois LLC vs corporation: what is the difference?

Online filing has limits. An LLC can form online if it is not formed in another state and does not need special purposes or provisions. A corporation can form online only if it has a single class of common stock, the general "any lawful purpose" statement, and is not a professional, medical, close or special-purpose corporation.

How do Illinois taxes differ?

Illinois taxes all entity types, but not in the same way. Current rates on the Department of Revenue rate page are:

• Individual income tax: 4.95% of net income, which reaches LLC members and S corporation shareholders on their pass-through income.
• Corporate income tax: 7% of net income for C corporations, plus personal property replacement tax of 2.5%.
• Replacement tax for partnerships, trusts and S corporations: 1.5% of net income, paid by the entity. An LLC taxed as a partnership files Form IL-1065; an S corporation files Form IL-1120-ST.

Filing dates also differ. IL-1120 and IL-1065 are due on the 15th day of the fourth month after year-end (April 15 for calendar-year filers), with automatic extensions of seven and six months. IL-1120-ST is due on the 15th day of the third month, with an automatic seven-month extension. For details see Illinois income tax for individuals and businesses.

How does the corporate franchise tax work?

Under Article 15 of the Business Corporation Act, a domestic corporation pays an initial franchise tax when it reports its first issuance of shares and an annual franchise tax with each annual report. The annual rate is one-tenth of one percent of paid-in capital allocated to Illinois, with a $25 minimum. The statute exempts the first $10,000 of liability for periods on and after January 1, 2025, so many small corporations owe little or nothing, but the filing fees remain. The Secretary of State will not file other documents for a corporation that is in default on franchise tax or that IDOR has reported as in default on a return, so a tax problem can freeze the corporate record.

Which federal tax classification can you pick?

Entity law and tax law are separate. The IRS treats a one-member LLC as disregarded and a multi-member LLC as a partnership unless it files Form 8832 to be taxed as a corporation. A corporation or an LLC can elect S status with Form 2553 if every requirement is met: a domestic entity, no more than 100 shareholders, one class of stock, and only individuals, certain trusts and estates as shareholders. Partnerships, corporations and nonresident alien shareholders are not allowed. The IRS calendar for 2026 shows the election due by March 16, 2026 for S status starting in 2026, and a late election starts in 2027.

An Indian resident or a Canadian resident who has not become a U.S. resident for tax purposes therefore cannot be a shareholder of an S corporation. A multi-member LLC taxed as a partnership, or a C corporation, is the usual alternative; see foreign-owned LLC U.S. tax and reporting and U.S. business entity types and tax forms.

How do you form each entity?

LLC

1. Search the name and confirm it carries an LLC designator.
2. Choose a registered agent in Illinois and a street-address registered office.
3. List each manager and any member with manager authority, with business addresses.
4. File Articles of Organization online or on form LLC-5.5 and pay $150.
5. Write an operating agreement. It is not filed, but the LLC must keep a member list, the articles, three years of tax returns, the operating agreement and three years of financial statements at its principal place of business.

Corporation

1. Search the name and add a corporate designator.
2. Decide authorized shares, issued shares and the consideration to be received; the franchise tax base comes from these figures.
3. Name an incorporator who is a natural person at least 18 years old.
4. File Articles of Incorporation with $150 and the initial franchise tax.
5. Hold an organizational meeting, adopt bylaws and issue shares.

Worked example

Rahul and Ananya, two Naperville engineers, expect a software consulting business to earn $240,000 of net profit in its first full year. As a two-member LLC taxed as a partnership, they pay $150 to form, $75 a year to report, and the entity pays 1.5% replacement tax on net income, about $3,600, with profit taxed to them personally at 4.95% in Illinois. As a C corporation, corporate-level tax in Illinois is 7% plus 2.5% on net income before any federal tax, and dividends would be taxed again. If both were U.S. residents, an S corporation could also work, which is a point to test against payroll costs. The numbers are illustrative only.

Mistakes to avoid

• Choosing a corporation only for its image when an LLC meets the need.
• Electing S status for an owner who is a nonresident alien.
• Forgetting that each series of a series LLC adds $50 to the annual report fee.
• Treating the operating agreement as optional; without one, the statute's default rules govern your business.
• Letting the annual report lapse; see annual report and registered agent rules.

How we can help

We work with owners in Aurora, Naperville and the surrounding Fox Valley on the U.S. side of entity choice: comparing state and federal tax results, preparing the Form 8832 or 2553 analysis, and setting up books and payroll. Where a Canadian CPA or an Indian Chartered Accountant is involved, we coordinate so the three sets of filings agree. Start with business formation and registrations and business tax returns and planning, or read the start-a-business checklist.

Frequently asked questions

General information only. It is not tax, legal, accounting or immigration advice for your situation, and rules change; confirm the current rules with the official source or a licensed professional in the relevant country.