How to Form an LLC in Illinois: What to File and When

To form a standard domestic LLC in Illinois, file Articles of Organization, Form LLC-5.5, with the Illinois Secretary of State, Department of Business Services, Limited Liability Division. The filing fee is $150. Before filing, choose a compliant LLC name, identify an eligible registered agent with an Illinois registered office, decide who will serve as organizer, and prepare the company information requested in the Articles.

The filing creates an important starting point, but it is not the end of the company’s administrative work. After formation, organize the LLC’s records, address any registrations relevant to its business activities, and track the Illinois annual report deadline. Every Illinois LLC must file Form LLC-50.1 before the first day of its anniversary month each year.

Key Illinois LLC formation requirements

A well-prepared filing begins with the company name, registered agent information, and organizer details. Confirming these items before completing the Articles can help prevent inconsistencies that require correction.

Choose an acceptable LLC name

The company name must be distinguishable on the Illinois Secretary of State’s records. It must contain “Limited Liability Company,” “L.L.C.,” or “LLC.” The name cannot contain Corporation, Corp., Incorporated, Inc., Ltd., Co., Limited Partnership, or L.P.

Check the complete proposed name rather than evaluating only its main words. Punctuation, abbreviations, and designators should be consistent wherever the name appears in the formation paperwork and in the company’s internal planning documents.

Select a registered agent and registered office

An Illinois LLC must maintain both a registered agent and a registered office in Illinois. The agent must be either an Illinois resident or a business entity authorized to transact business in Illinois. The registered office must use an Illinois street address or a qualifying rural-route address, and it must match the registered agent’s business-office address.

Before listing an agent, verify the exact spelling of the agent’s name and the complete address. A mailing address used elsewhere by the business should not automatically be treated as the registered-office address. Use the address that satisfies the registered-office rules and corresponds to the selected agent.

Identify the organizer or organizers

An Illinois LLC may have one or more organizers. An organizer may be an individual who is at least 18 years old or a business entity. Each organizer must sign the Articles of Organization.

The organizer completes and signs the formation filing, but that role should not be confused with every other role in the business. When preparing the filing, separately identify the people or entities involved and use the correct information in each part of the form.

How to file the Articles of Organization

1. Decide whether the company is a standard LLC or a series LLC. A standard domestic Illinois LLC uses Form LLC-5.5. A domestic series LLC uses Form LLC-5.5(S) instead. Do not choose a form solely because the business may have multiple products, locations, or projects; first determine the intended legal structure.
2. Finalize the company name. Confirm that the name includes an approved LLC designator, avoids prohibited corporate and limited-partnership terms, and is distinguishable on the Secretary of State’s records.
3. Confirm the registered agent and office. Obtain accurate information from the selected agent and make sure the Illinois office address matches the agent’s business-office address.
4. Prepare the remaining company and organizer information. Keep spelling, addresses, and formatting consistent. Every organizer named as an organizer must sign the Articles.
5. Select a filing method and prepare the correct submission. Paper filers must submit Form LLC-5.5 in duplicate: one originally signed document and one additional original or photocopy. That duplicate-copy instruction applies to paper filing and should not be treated as an online-filing requirement.
6. Pay the applicable fee. The filing fee for standard Form LLC-5.5 is $150. An additional $100 fee applies when expedited service is requested. Expedited requests may be made online or in person, but mailed requests cannot be expedited.
7. Retain the completed filing and related records. Preserve a copy of what was submitted, proof of payment, and the returned formation documentation in the LLC’s records. This creates a reliable reference when the business later handles banking, tax, licensing, or reporting matters.

If the broader setup involves more than the entity filing, the guide to registering a business in Illinois can help organize the other parts of the launch without mixing them into the Articles of Organization.

Standard LLC and series LLC filing differences

The standard and series forms are not interchangeable. A standard domestic Illinois LLC files Form LLC-5.5 and pays a $150 filing fee. A domestic Illinois series LLC files Form LLC-5.5(S) instead and pays a $400 filing fee. When expedited service applies to a series LLC filing, the additional expedited fee is $100.

Because the series choice affects both the form and the fee, make the structural decision before preparing a filing. If the business plan does not clearly establish whether a series structure is appropriate, obtain advice suited to the ownership, liability, and operational arrangement before submitting the Articles. Correcting an uncertain structural choice after filing can be more complicated than resolving it at the planning stage.

Practical mistakes to avoid

• Using a name without an accepted LLC designator. Build “Limited Liability Company,” “L.L.C.,” or “LLC” into the exact name intended for the filing.
• Including a prohibited business designation. Review the entire name for prohibited corporate or limited-partnership terms, not just the ending.
• Listing an unsuitable registered-office address. Confirm that the address is an Illinois street or qualifying rural-route address and that it matches the registered agent’s business-office address.
• Confusing the registered agent with the organizer. Treat these as separate entries and verify the information required for each role.
• Missing an organizer’s signature. If the Articles identify multiple organizers, each organizer must sign.
• Sending only one paper copy. Paper Form LLC-5.5 submissions must be filed in duplicate, including an originally signed document and an additional original or photocopy.
• Expecting expedited treatment for a mailed filing. Expedited requests may be made online or in person; they are not available for mail requests.
• Using the standard form for a series LLC. A domestic series LLC must use Form LLC-5.5(S), not standard Form LLC-5.5.
• Treating formation as the final administrative step. Keep a calendar for recurring reports and identify any tax or operational registrations relevant to what the company actually does.

Avoid copying information from informal notes without checking it. A final review should compare the company name, registered agent name, office address, organizer information, signatures, filing form, and fee as one complete submission.

What to do after filing

Once the formation documentation is available, store it with the LLC’s core records and use the company name consistently. Internal organization may include documenting ownership and management arrangements, separating business records from personal records, and establishing a process for preserving important correspondence. The appropriate documents and procedures depend on the company’s ownership and operations.

If the LLC needs a federal employer identification number, review the Illinois EIN guide for LLCs. An EIN application is separate from filing the Illinois Articles of Organization, so information should be checked for consistency across the two processes.

Businesses that make taxable sales may also need to examine Illinois tax-registration issues based on their activities. The overview of an Illinois sales tax number provides a separate starting point for that question. Tax registration, licensing, and permit needs should be evaluated according to the company’s activities and location rather than assumed to apply identically to every LLC.

Finally, calendar the annual report. Every Illinois LLC must file Form LLC-50.1 before the first day of its anniversary month each year. The annual report filing fee is $75. If the report is not filed within 60 days after its due date, a $100 penalty applies. Record the deadline in more than one reliable place and keep the registered-agent and company contact information organized so recurring compliance work is not overlooked.