To start an LLC in Illinois, file Articles of Organization (LLC-5.5) with the Illinois Secretary of State, Department of Business Services, for $150 (as of October 2026), naming a registered agent with an Illinois address. Then sign an operating agreement, get an EIN and register for Illinois taxes. Each year, the LLC files a $75 annual report before the first day of the month in which it was formed.
Illinois also offers a series LLC, which lets one LLC hold separate “series” with their own assets. It costs more to form, $400, but some real estate investors and holding companies find it worth it. Most small businesses choose the standard LLC.
Updated October 2026.
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Best LLC Formation Services in Illinois (2026)
Our ranked picks for forming an LLC in Illinois are below, starting with Mainstay Filing. Each entry lists the yearly price and what the service covers.
| Rank | Provider | Best for | Price | What’s included |
|---|---|---|---|---|
| 1 | Mainstay Filing | Forming an LLC with the agent, EIN and annual report included | $199/year + state fee at cost | LLC formation filing, registered agent for the year, EIN application, annual report preparation and filing |
| 2 | IL Registered Agent.org | Illinois registered agent service only | $99/year | $99 per year, flat; in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online |
| 3 | Illinois Registered Agent.co | Illinois registered agent service only | $99/year | in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online |
1. Mainstay Filing
Mainstay Filing is our top pick in Illinois. It costs $199/year + state fee at cost and covers lLC formation filing, registered agent for the year, EIN application, annual report preparation and filing. The price stays the same every year, with no add-on menu.
2. IL Registered Agent.org
IL Registered Agent.org is a Illinois registered agent service at $99/year. It provides $99 per year, flat; in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online. It’s a fit if you only need a registered agent rather than full formation help.
3. Illinois Registered Agent.co
Illinois Registered Agent.co is a Illinois registered agent service at $99/year. It provides in-state street address for the registered office; legal documents served on the company are scanned and sent to the owner online. It’s a fit if you only need a registered agent rather than full formation help.
Illinois LLC at a glance
| Item | Illinois (as of October 2026) |
|---|---|
| Filing office | Illinois Secretary of State, Department of Business Services |
| Formation document | Articles of Organization (LLC-5.5) |
| Filing fee | $150 (series LLC: $400 with LLC-5.5(S)) |
| Annual report | $75; due before the first day of the anniversary month |
| Late annual report | $100 penalty |
| Registered agent | Illinois resident or registered business entity; LLC can’t be its own agent |
| Agent change | $25 (LLC-1.36/1.37) |
| State tax note | 1.5% replacement tax on partnership income |
| Publication | Not required |
Formation rules are in 805 ILCS 180/5-5; annual report details are in the Secretary of State’s LLC annual report instructions. Mainstay Filing’s Illinois LLC cost page shows state fees next to service costs.
How do you pick a name for an Illinois LLC?
Your name needs “Limited Liability Company,” “LLC” or “L.L.C.” and must be distinguishable from other names on the Secretary of State’s records. Illinois also restricts certain words, such as those suggesting banking or insurance, unless you meet the related licensing rules.
Use the namechk business name generator to build a list, then check each name in the Secretary of State’s LLC database search. Our Illinois business name search guide explains how to search for close variations.
Before filing:
- Search federal trademarks in the USPTO database.
- Confirm the domain and social handles with namechk.
- Plan for an assumed name filing if you’ll trade under a name other than the LLC’s legal name, and confirm with the Secretary of State and your county clerk where it must be filed.
Who can be your Illinois registered agent?
Under 805 ILCS 180/1-35, every Illinois LLC must continuously maintain a registered agent and registered office in Illinois. The Secretary of State’s forms spell out the rules: the agent must reside in Illinois, a business entity acting as agent must be registered with the Secretary of State, and the LLC may not act as its own registered agent.
The registered office must be an Illinois address identical to the agent’s business office, and a P.O. box alone isn’t acceptable. If your agent resigns, the LLC has 60 days to appoint a new one before a $100 penalty applies.
You can serve as your own agent if you live in Illinois and can accept legal papers during business hours. Otherwise, use a professional service. Mainstay Filing includes a year of registered agent service with its formation package, and our Illinois registered agent guide covers the details. Changing agents later costs $25.
How do you file Illinois Articles of Organization?
File LLC-5.5 online through the Secretary of State’s website or on paper, submitting paper filings in duplicate. The $150 fee applies either way. The Articles ask for:
- The LLC’s name
- The principal place of business address
- The registered agent’s name and registered office address
- The purpose of the LLC (Illinois accepts “any lawful purpose”)
- Whether the LLC is managed by managers or by members, with their names and addresses
- The organizer’s name, address and signature
For a series LLC, use the LLC-5.5(S) version of the Articles and pay $400 instead. Whichever version you file, keep a copy of the filed Articles with your records; banks ask for it when you open the business account, and you’ll need the LLC’s file number for the annual report.
Do you need an operating agreement in Illinois?
Illinois doesn’t require you to file an operating agreement, and the Secretary of State won’t ask for one. It still sets the rules that matter most: ownership, contributions, management, voting, distributions and member exits.
If you form a series LLC, the operating agreement is where each series is defined, so it’s essential there. For any LLC, a written agreement helps show that the company is separate from its owners.
How do you get an EIN and register for Illinois taxes?
Apply for an Employer Identification Number on the IRS website; it’s free. Then register with the Illinois Department of Revenue through MyTax Illinois if you’ll collect sales tax or withhold wages, and with the Illinois Department of Employment Security if you’ll have employees.
One Illinois-specific tax to know: LLCs taxed as partnerships owe a 1.5% personal property replacement tax on their income, filed with the partnership return. Talk to your accountant about how it applies to you, since it’s easy to overlook when you’re focused on the federal return and it applies even to small LLCs.
FinCEN’s beneficial ownership page states that U.S.-formed companies are exempt from BOI reporting under the final rule effective August 2026.
When is the Illinois LLC annual report due?
Illinois LLCs file an annual report every year before the first day of their anniversary month, meaning the month the LLC was formed. You can file during the 60 days before that date. The fee is $75, online or on paper, through the Secretary of State’s online annual report service.
Online filing is limited to LLCs with eight or fewer members; larger LLCs, filings signed under a power of attorney and reinstatements use paper LLC-50.1. A $100 late penalty applies once a report is 60 days past due, and an LLC that stays delinquent can be administratively dissolved.
What licenses does an Illinois LLC need?
Illinois has no general statewide business license. Cities and counties often require local licenses, and many professions need a state license from the Illinois Department of Financial and Professional Regulation. Chicago, for example, has its own business licensing system, so check with your municipality before opening. Some home-based businesses also need zoning approval, so ask about that when you contact your city or county.
Illinois LLC FAQs
How much does it cost to start an LLC in Illinois?
The Illinois Secretary of State charges $150 to file Articles of Organization on LLC-5.5, as of October 2026. A series LLC costs $400 using LLC-5.5(S). After formation, every Illinois LLC files a $75 annual report each year, and a late report adds a $100 penalty.
When is the Illinois LLC annual report due?
An Illinois LLC’s annual report is due before the first day of its anniversary month, the month it was formed. It can be filed during the 60 days before that date. The fee is $75, and a $100 penalty applies once the report is 60 days past due.
What is an Illinois series LLC?
A series LLC is a single Illinois LLC that can establish separate series, each with its own assets and members, under one formation filing. It’s formed with LLC-5.5(S) for $400 instead of $150. The operating agreement defines each series, so careful drafting is essential.
Can my Illinois LLC be its own registered agent?
No. The Illinois Secretary of State’s forms state that an LLC may not act as its own registered agent. The agent must be an Illinois resident or a business entity registered with the Secretary of State, with a registered office in Illinois that isn’t just a P.O. box.
What is the Illinois replacement tax for LLCs?
Illinois charges a personal property replacement tax on the income of partnerships, which includes LLCs taxed as partnerships, at 1.5%. It’s reported with the Illinois partnership return. LLCs taxed as corporations pay the corporate rate instead, so check with a tax professional about your LLC’s situation.
Can I file the Illinois annual report online?
Yes, if your LLC has eight or fewer members. The Secretary of State’s online annual report service handles most filings for $75. LLCs with more than eight members, reports signed under a power of attorney, and reinstatements must use the paper LLC-50.1.
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