How to Complete and File Illinois Series LLC Articles of Organization (LLC-5.5(S))

To form a Series LLC in Illinois, file Articles of Organization on Form LLC-5.5(S) with the Secretary of State for a $400 filing fee, either online at apps.ilsos.gov or by mail to the Springfield office.¹ That filing creates the master entity. Each individual series underneath it needs its own Certificate of Designation on Form LLC 37.40, at $50 per series, before that series gets statutory liability protection.² Treat the Articles as step one of two.

A Series LLC is a single registered entity that can house separate series underneath it, each able to own property, enter contracts, sue or be sued, and have its own members and managers without being separately registered. If one series is sued or takes on debt, creditors can reach only that series’ assets, not the master LLC or the other series — provided every statutory box is checked.²

What You Need Before You Open the Form

Gather this information first. A missing field will stall or reject the filing.

LLC Name

The name must include “Limited Liability Company,” “L.L.C.,” or “LLC,” and must be distinguishable from any existing entity on file with the Secretary of State.³ Check availability through the Secretary of State’s online business name database before you file.

Principal Place of Business

Give the address of the primary location where the company directs operations and keeps its books. This address does not need to be in Illinois.⁴ It is a separate field from the registered office.

Registered Agent and Registered Office

Every Illinois LLC must maintain a registered agent at a registered office in the state.⁵ The agent accepts legal papers and official notices for the LLC. The office must be a physical street address; P.O. boxes are not acceptable. The agent has to sign the form to accept the appointment, so coordinate before filing.

You can serve as your own agent if you have an Illinois address and are reliably available during business hours. Commercial registered agent services typically charge between $35 and $200 per year and reduce the risk of missing a lawsuit filing or a state notice.

Organizer Information

List the name and address of each organizer. The organizer is the person actually executing the filing and does not need to be a member or manager.⁴

Management Structure

Choose member-managed or manager-managed. In a member-managed LLC, all owners share decision-making. In a manager-managed LLC, one or more designated managers run the business while other members take a passive role. If you choose manager-managed, list the name and business address of at least one manager; if member-managed, list every member with management authority.⁴ Changing this choice later requires an amendment.

Purpose, Duration, and Effective Date

Most organizers state the purpose in broad terms, such as “any lawful act for which a limited liability company may be organized,” so operations can shift without amending the Articles. Duration defaults to perpetual unless you specify an end date. The effective date can be the filing date or a future date up to 60 days after the Secretary of State processes the filing; leaving it blank defaults to the filing date.⁴ A delayed effective date is useful for coordinating with a closing or the start of a quarter.

The Series Liability Notice: Why Form LLC-5.5(S) Is Not the Standard Form

Under 805 ILCS 180/37-40, the Articles of Organization for a Series LLC must contain a notice stating that the debts, liabilities, and obligations of one series are enforceable only against the assets of that series, not against the master LLC or any other series.² Form LLC-5.5(S) contains this language. The standard Form LLC-5.5 does not. File the wrong one and you have a standard LLC with no series protection, fixable only by amendment.

Filing a Certificate of Designation for Each Series

The Articles of Organization create the master LLC. They do not activate liability protection for any individual series. Each series must have its own Certificate of Designation on Form LLC 37.40 filed with the Secretary of State before the statutory shield applies to it.² The certificate costs $50 per series.¹

The certificate must include the name of each series with limited liability. If a series has different managers or members with management authority than the master LLC, those names and business addresses must also appear on the certificate.² A series legally exists once the Secretary of State files the certificate. You can file Certificates of Designation at the same time as the Articles or add new series later. Budget the $50 per series into your formation costs from the start.

How to Submit the Form

Online

The Secretary of State accepts filings through its LLC Articles of Organization portal at apps.ilsos.gov.⁶ The system walks through each required field and takes electronic payment. Online filings generally process faster than paper.

By Mail

Send the completed Form LLC-5.5(S) with payment to:

Secretary of State
Department of Business Services
501 S. Second Street, Room 350
Springfield, IL 62726

Make checks or money orders payable to the Secretary of State. The filing fee is $400, plus $50 for each Certificate of Designation you include with the initial filing.¹ Expect several weeks for standard mail processing.

Expedited Processing

Expedited service costs an additional $100 on top of the $400 filing fee, and an additional $50 per Certificate of Designation.¹ Worth it if a real estate closing or similar deadline is driving the timing.

After Approval

Once the Secretary of State approves the filing, you receive a file-stamped copy of the Articles of Organization. That document is your legal proof the LLC exists and is authorized to do business in Illinois. Keep it with the operating agreement in your permanent records.

After Filing: Keeping the Liability Shield Intact

Operating Agreement

Illinois does not require you to file an operating agreement with the state, but for a Series LLC it is effectively mandatory. The statute ties series liability protection directly to the operating agreement: it must establish the series, define each series’ separate rights and duties, and provide that each series’ liabilities are limited to its own assets.² Without those provisions, even a properly filed Certificate of Designation may not hold up.

The agreement should address how new series are created, how each series is managed, how assets are allocated between series, and what happens when a series is dissolved. For a multi-member Series LLC, working with an attorney on this document is money well spent.

Separate Records and Bank Accounts for Each Series

The shield between series depends on keeping separate and distinct records for each one. Each series needs its own bank account, its own books, and its own accounting for assets and liabilities.² Commingling funds across series, or between a series and the master LLC, is the fastest way to lose the protection you paid for. A court looking at mixed accounts and sloppy records has little reason to respect the series boundaries.

EINs

The master LLC needs its own Employer Identification Number from the IRS, and each series should obtain a separate EIN as well. A separate EIN lets each series open its own bank account and file its own tax returns if treated as a separate entity for federal tax purposes. Apply at irs.gov at no cost.

Annual Report

Illinois requires every LLC to file an annual report with the Secretary of State to remain in good standing. The report is due before the first day of the LLC’s anniversary month — the month in which the Articles of Organization were filed. Missing it brings penalties and eventually administrative dissolution, which strips the LLC of its authority to do business and can expose members to personal liability for obligations incurred after dissolution. Annual reports can be filed online.

Common Mistakes That Derail a Series LLC Filing

Filing Form LLC-5.5 instead of Form LLC-5.5(S). The standard form lacks the series liability notice, and the only fix is an amendment.
Treating the Articles as the whole filing. Each series needs its own $50 Certificate of Designation on Form LLC 37.40 before it has liability protection.
Using a generic LLC operating agreement, or none at all. The statute requires the agreement to create the series and provide for their limited liability.
Commingling assets across series or with the master LLC, which undermines the separate-records requirement the statute demands.
Listing a P.O. box as the registered office. The office must be a physical Illinois street address, and a filing with a P.O. box will be rejected.

1
Illinois Secretary of State. Limited Liability Company Publications and Forms
2
Illinois General Assembly. Illinois Compiled Statutes 805 ILCS 180/37-40
3
Illinois General Assembly. Illinois Compiled Statutes 805 ILCS 180/1-10
4
Illinois General Assembly. Illinois Compiled Statutes 805 ILCS 180/5-5
5
FindLaw. Illinois Code 805 ILCS 180/1-35
6
Illinois Secretary of State. LLC Articles of Organization