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How do I form an LLC in Illinois?

Federal & State Law Editorial TeamLast reviewed: 2026-04-30

Illinois LLCs are governed by the Illinois Limited Liability Company Act, 805 ILCS 180/.

1. Filing Fee and Processing Time

  • Articles of Organization (Form LLC-5.5): $150 filing fee with the Illinois Secretary of State, Department of Business Services.
  • Processing: ~10 business days online; longer by mail. Expedited 24-hour filing available for an extra $100.

    • 2. Name Reservation

  • Optional. 90-day reservation for $25 (Form LLC-1.15). Name must include "Limited Liability Company," "LLC," or "L.L.C." (805 ILCS 180/1-10).

    • 3. Registered Agent

  • Required under 805 ILCS 180/1-35.
  • Must be an Illinois resident individual OR an entity authorized to do business in Illinois, with an Illinois street address.

    • 4. Operating Agreement

  • Not required to be filed or even adopted (805 ILCS 180/15-5), but strongly recommended.
  • May be oral, written, or implied. The Act provides default rules.

    • 5. Annual Report

  • Required. Due each year by the first day of the LLC's anniversary month (e.g., LLC formed March 15 — report due March 1 each year).
  • Filing fee: $75 (reduced from $250 in 2018).
  • Late penalty: $100 plus possible administrative dissolution after 60 days.

    • 6. State Taxes

  • Illinois has a flat 4.95% personal income tax.
  • LLCs taxed as partnerships or S-corps pay the Personal Property Replacement Tax (PPRT) at 1.5% of net income (35 ILCS 5/201(d)).
  • LLCs taxed as C-corporations pay 9.5% combined corporate income tax + PPRT (7% income + 2.5% replacement).

    • 7. Series LLCs

  • Illinois recognizes Series LLCs under 805 ILCS 180/37-40. Each series must be designated in the Articles or in a Certificate of Designation. Each series files its own annual report.

    • 8. Federal EIN and Illinois Registration

  • Obtain federal EIN from IRS (free).
  • Register with the Illinois Department of Revenue (Form REG-1) for tax accounts.
  • Register with the Illinois Department of Employment Security if hiring employees.

    • 9. Local Licenses

  • Chicago and many other Illinois municipalities require local business licenses.

    • This is legal information, not legal advice.

    When to Talk to a Lawyer
    • You want to form a Series LLC in Illinois
    • You are operating in Chicago and need to navigate municipal licensing
    • You are converting from a sole proprietorship and need entity-classification advice
    Related Statutes & Laws
    • 805 ILCS 180/1-10
    • 805 ILCS 180/1-35
    • 805 ILCS 180/15-5
    • 805 ILCS 180/37-40
    • 805 ILCS 180/50-1
    • 35 ILCS 5/201(d)

    This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.