Illinois Series LLC: The $400 Filing, How Each Series Works and When to Use One

Most business owners think of an LLC as a single entity. An Illinois series LLC is different. It's one LLC that holds multiple separate series within it, each with its own assets, liabilities, and operations. Each series operates independently, yet they share the same Articles of Organization and registered agent. For the right business model, a series LLC cuts filing costs dramatically and simplifies portfolio management.

What Is a Series LLC and Why Illinois Allows Them

A series LLC is a special type of limited liability company authorized under Illinois law (805 ILCS 180/37 through 180/40). The structure lets you create independent series within a single LLC. Each series is legally distinct: it holds its own assets, incurs its own debts, and operates under its own business purpose. The series are shielded from each other. If one series faces a lawsuit or creditor claim, the other series and the parent LLC remain protected.

Illinois is one of a small number of states that permit series LLCs. Delaware, Nevada, and a handful of others offer the same structure. The concept appeals to landlords managing multiple rental properties, business owners operating separate product lines, or investors holding diverse assets. Instead of filing separate LLC articles for each venture, you file one set of articles and add series as needed.

The $400 Filing Cost and What You Actually Pay

An Illinois series LLC costs $400 to file. This is the Articles of Organization fee, the same form you would use for a standard LLC, but designated as a series LLC on the document. This $400 base fee is a one-time cost for the parent LLC structure.

Here's where the cost model becomes attractive: each additional series within the parent LLC requires a separate filing. You must file a Certificate of Designation for each series with the Illinois Secretary of State. The Certificate of Designation fee is $50 per series. So if you want to establish three rental property series within one parent LLC, you pay:

• Articles of Organization (parent series LLC): $400
• Certificate of Designation (Series 1): $50
• Certificate of Designation (Series 2): $50
• Certificate of Designation (Series 3): $50
• Total: $550 for the parent LLC and three separate property series.

By contrast, filing three separate standard LLCs would cost $150 each, totaling $450 before you account for multiple registered agents, multiple annual reports, and separate filings year after year. The longer you operate, the more the series LLC saves you.

Processing time for series LLC filings is 10 business days for standard online filing through the Illinois Secretary of State at https://apps.ilsos.gov/llcarticles/index.jsp. If you need faster approval, expedited service is available: $500 total for the Articles of Organization ($400 base plus $100 expedite surcharge) or $100 total for a Certificate of Designation ($50 base plus $50 expedite surcharge) to get approval in 24 hours.

How Each Series Actually Works

A series LLC is structured like a holding company with internal divisions. Assets are typically titled to specific series. Under 805 ILCS 180/37-40, a series with limited liability is treated as a separate entity to the extent set forth in the articles of organization. Each holds title to its own property, enters into contracts in its own name, and maintains separate bank accounts and financial records.

Consider a real estate investor with four rental properties in different neighborhoods. Instead of four separate LLCs, the investor can create:

• Riverside Properties LLC (parent)
• Series A: Downtown Apartment
• Series B: Suburban House
• Series C: Commercial Space
• Series D: Vacant Land

Each series owns its property, collects its rent, and pays its expenses. The landlord files one set of annual reports with the Secretary of State, but the annual report cost reflects each active series: the base $75 annual report for the parent, plus $50 for each active series. So the investor would pay $75 plus $50 times 4 series, or $275 total, versus $75 times 4 separate LLCs at $300.

More important than the fee savings: the series structure simplifies property management. One operating agreement covers all series. One registered agent and one principal business address serve all of them. One member or manager can oversee the entire portfolio. Yet if a tenant sues over the Downtown Apartment property, that lawsuit touches only Series A. Series B, C, D, and the parent remain unaffected and protected.

Liability Shield: The Rules You Must Follow

The liability separation is not automatic. Illinois law states that each series is protected from the debts and liabilities of other series and the parent, but only if you follow strict requirements. These are not optional:

1. Separate Records: Each series must maintain its own books, financial records, and legal documents. These records must be kept separate and distinct from the parent and other series. A creditor must be able to see that Series A's assets and liabilities were never comingled with Series B's.
2. Separate Assets: Title each series's assets in that series's name. If Series A owns a rental property, the deed must be titled to the series, not the parent LLC. Bank accounts must be established for each series, separate from the parent and other series accounts. Do not transfer assets between series without clear documentation.
3. Operating Agreement Language: The LLC's operating agreement must explicitly provide for series and the maintenance of separate series assets and records. If the operating agreement does not mention series, or is silent on how assets are allocated and records maintained, the liability shield may not hold.
4. Notice in Articles: The Articles of Organization must reference the existence of series or provide authority for series. The Secretary of State provides a form for series LLCs. When you file, the form must be marked to indicate this is a series LLC. Failing to do so may invite a creditor to argue the series shield does not apply.

The statute is found at 805 ILCS 180/37 through 180/40. If you ignore these rules, a court may "pierce" the series shield and hold you personally liable or impose liability across series. Do not treat the separate series structure as a formality.

When a Series LLC Makes Sense

A series LLC is ideal for landlords and investors managing multiple rental properties. Each property series holds its deed, collects rent, and carries its own insurance. If a tenant in the Downtown series sues, the Suburban and Commercial series are not dragged into the lawsuit. The structure also reduces administrative burden: one annual report filing and one operating agreement.

Series LLCs also work for small business owners running multiple product lines or service divisions. If you sell both consulting services and software, you might create a Consulting series and a Software series. The services operate under separate brand names, manage separate client bases, and if a product liability claim hits the Software series, the Consulting series and revenue remain protected.

Series LLCs are less ideal if you have only one venture or if your series will hold only passive investments. A single-purpose LLC is simpler and costs less to file. Series LLCs also require discipline in record-keeping. If you cannot maintain separate accounting and records for each series, the liability shield weakens or fails. The upfront burden of proper bookkeeping must be worth the liability and tax benefit you gain.

Ongoing Costs and Annual Compliance

Each year, the series LLC must file a Limited Liability Company Annual Report (Form LLC-50.1) with the Illinois Secretary of State. The parent LLC's annual report costs $75. For each active series, add $50 to that fee. The report is due before the first day of the LLC's anniversary month, the month in which the Articles of Organization were originally filed. A pre-filled report is mailed to your registered agent about 45 days before the due date.

Late filing carries a penalty: if the report is not filed before the first day of the anniversary month the LLC is not in good standing, and a $100 penalty applies if the default is not cured before the first day of the second month after the anniversary month, plus $100 for each further year of delinquency (805 ILCS 180/50-15). So if your anniversary month is March, the report is due before March 1. If you file it on May 15, you owe the $75 base annual report fee plus the $100 late penalty.

Illinois imposes no state franchise tax on LLCs. An LLC taxed as a partnership (the default) pays a 1.5 percent personal property replacement tax on net income. An LLC that elects corporate tax treatment pays a 7 percent corporate income tax plus a 2.5 percent replacement tax. For a series LLC, the same rules apply to each series based on how it is taxed.

Your series LLC must maintain a registered agent and a registered office address in Illinois. The registered agent must be either an individual living in Illinois or a business entity authorized to transact business in Illinois. The registered office must have a street or road address (not a P.O. Box alone). Changing the registered agent or office costs $25. Many owners use a professional registered agent service to handle service of process and mail receipt.

Series LLC vs. Multiple Separate LLCs: The Comparison

Suppose you own five rental properties and want to structure them for liability protection. Your choices are a series LLC or five separate standard LLCs.

Series LLC approach: One $400 filing for the parent Articles of Organization, plus $50 for each of five Certificates of Designation, equals $650 upfront. Annual report costs: $75 base plus $50 times 5 series, equals $325 per year. You file one set of documents, maintain one registered agent, and one operating agreement covers all five properties.

Five separate LLC approach: Five filings at $150 each, equals $750 upfront. Annual reports: $75 times 5, equals $375 per year. You need five registered agents (or five registered agent entries for one service), five operating agreements, and five separate accounting records.

Over five years, the series LLC saves $100 upfront ($650 versus $750) and $50 per year in annual report fees ($325 versus $375), about $350 in cumulative savings. The series LLC also centralizes management and administration.

The trade-off: the series LLC requires discipline in maintaining separate records and keeping assets separate for each series. If you fail to follow the rules, the liability shield fails. A separate LLC is simpler if you lack the accounting infrastructure or the inclination to maintain strict series separation.

How to File a Series LLC in Illinois

File your series LLC Articles of Organization online through the Illinois Secretary of State's business filing portal at https://apps.ilsos.gov/llcarticles/index.jsp. The form is titled Articles of Organization (Form LLC-5.5). Mark the form to indicate this is a series LLC. Include language in the articles or articles of amendment authorizing series, or provide a brief description of the series structure.

The Articles must include the LLC name (which must include "Limited Liability Company," "LLC," or "L.L.C."), the name and street address of the registered agent and registered office in Illinois, the name and street address of at least one manager or member, and the effective date (or it defaults to the filing date).

Once the parent LLC is approved, file a Certificate of Designation for each series. The form is available from the Secretary of State. Each Certificate names the series, references the parent LLC, and specifies the series's purpose and any relevant details. The $50 fee applies to each Certificate.

Processing is 10 business days for standard online filing. You can check the status of your filing at https://apps.ilsos.gov/businessentitysearch/. If you need the filing faster, pay the expedite surcharge for 24-hour processing.

Important Disclaimer

This guide is informational only and not legal or tax advice. Series LLC structures involve complex legal and tax considerations. Before filing, consult a qualified Illinois business attorney to ensure your operating agreement, series designations, and asset titling comply with state law and protect you as intended. Consult a CPA or tax advisor to understand the tax implications for your specific situation, including entity classification, series taxation, and state and federal filing requirements. Do not rely on this article as a substitute for professional guidance.

Next Steps

If a series LLC fits your business model, start by reviewing the Illinois Secretary of State's LLC forms and instructions at https://www.ilsos.gov/departments/business-services.html. Confirm the current Articles of Organization form, Certificate of Designation form, and filing fees. Then consult an attorney and tax professional to draft your operating agreement, establish your series structure, and plan your asset titling and accounting.

For additional business formation support, contact the Illinois Small Business Development Center at https://sbdc.illinois.gov/ or the U.S. Small Business Administration District Office for Illinois at https://www.sba.gov/district/illinois.