How to Form S-Corp in Illinois

Quick Answer

To form an S-Corporation in Illinois, you must first incorporate as a regular corporation with the Illinois Secretary of State for a $150 filing fee, then file Form 2553 with the IRS to elect S-Corp tax status. As of April 10, 2026, processing time is 5-10 business days for standard filings. Illinois requires a registered agent and imposes a 4.95% flat income tax rate on S-Corp income.

Step-by-Step Formation Process

1. Choose and Reserve Your Corporate Name

   • Verify name availability through the Illinois Secretary of State’s business search
   • The name must include “Corporation,” “Incorporated,” “Company,” or an abbreviation
   • Consider reserving the name for 120 days if not filing immediately

2. Appoint a Registered Agent

   • Designate an Illinois resident or business entity authorized to conduct business in Illinois
   • The registered agent must have a physical Illinois address (not a P.O. Box)

3. File Articles of Incorporation

   • Complete and file Form BCA-2.10 with the Illinois Secretary of State
   • Include corporate name, registered agent information, and authorized shares
   • Pay the $150 filing fee
   • File online at the Illinois Secretary of State website or by mail

4. Obtain Federal EIN

   • Apply for an Employer Identification Number through the IRS website
   • This is required before filing the S-Corp election

5. File S-Corporation Election

   • Submit IRS Form 2553 within 75 days of incorporation or by March 15 of the tax year
   • All shareholders must sign the form
   • File directly with the IRS, not the state

6. Create Corporate Bylaws

   • Draft internal governing documents (not filed with the state)
   • Establish shareholder and director procedures

7. Hold Initial Board Meeting

   • Adopt bylaws, elect officers, and authorize stock issuance
   • Document decisions in corporate minutes

Costs Breakdown

Item	Cost	Notes
Articles of Incorporation	$150	Illinois Secretary of State filing fee
Name Reservation (optional)	$25	Valid for 120 days
Registered Agent Service	$100-300/year	If using professional service
Federal EIN	Free	Apply directly with IRS
S-Corp Election (Form 2553)	Free	Must file with IRS
Certified Copies	$25 each	If needed for banking

Fees current as of April 10, 2026. Contact the Illinois Secretary of State for the most current fee schedule.

Requirements Checklist

Before filing your Articles of Incorporation, ensure you have:

• Unique Corporate Name - Must be distinguishable from existing Illinois entities
• Registered Agent - Illinois resident or authorized business entity
• Incorporator - Person 18+ who signs the Articles of Incorporation
• Initial Directors - At least one director required
• Authorized Shares - Determine number and type of shares to authorize
• Principal Office Address - Can be in or outside Illinois
• Filing Fee - $150 payable to Illinois Secretary of State

Tax Implications

Federal Tax Treatment S-Corporations are pass-through entities, meaning business income and losses flow through to shareholders’ personal tax returns. The corporation itself generally doesn’t pay federal income tax.

Illinois State Taxes

• Personal Income Tax: Illinois imposes a 4.95% flat income tax rate on S-Corp income passed through to shareholders
• Replacement Tax: S-Corps pay a 1.5% replacement tax on net income
• Sales Tax: Base rate of 6.25% applies to taxable goods and services
• No Franchise Tax: Illinois does not impose a franchise tax on corporations

Self-Employment Tax S-Corp shareholders who work in the business must take reasonable salary subject to payroll taxes. Distributions beyond salary are not subject to self-employment tax, providing potential tax savings.

Ongoing Obligations

Annual Reports

• File annual reports with the Illinois Secretary of State
• Due date varies by corporation’s anniversary month
• Filing fee: $75 as of April 2026
• Can be filed online through the Secretary of State’s website

Tax Filings

• File federal Form 1120S annually by March 15 (or 15th day of 3rd month after fiscal year-end)
• File Illinois Form 1120-ST for replacement tax
• Issue Schedule K-1 to all shareholders

Corporate Maintenance

• Hold annual shareholder meetings
• Maintain corporate records and meeting minutes
• Update registered agent information when necessary
• File amended articles if making structural changes

Registered Agent

Illinois law requires all corporations to maintain a registered agent with a physical address in the state. The registered agent serves legal documents and official correspondence on behalf of the corporation.

Registered Agent Options:

1. Yourself - Must be an Illinois resident with a physical address
2. Another Individual - Illinois resident willing to serve
3. Professional Service - Registered agent companies typically charge $100-300 annually

Registered Agent Responsibilities:

• Accept service of legal documents
• Forward important state correspondence
• Maintain regular business hours at the registered address
• Notify the state of any address changes

The registered agent’s name and address appear in public records, so many business owners prefer using a professional service for privacy.

Common Mistakes to Avoid

1. Missing the S-Corp Election Deadline File Form 2553 within 75 days of incorporation or by March 15 of the tax year to avoid waiting until the next tax year.

2. Inadequate Capitalization Ensure sufficient startup capital and document all contributions properly to maintain corporate protection.

3. Mixing Personal and Business Finances Maintain separate business bank accounts and avoid using corporate funds for personal expenses.

4. Failing to Pay Reasonable Salary S-Corp shareholders who work in the business must receive reasonable compensation subject to payroll taxes.

5. Neglecting Corporate Formalities Hold required meetings, maintain minutes, and follow bylaws to preserve limited liability protection.

6. Ignoring Annual Report Requirements File annual reports on time to avoid penalties and potential administrative dissolution.

7. Improper Stock Ownership S-Corps are limited to 100 shareholders, one class of stock, and specific shareholder eligibility requirements.

Related Guides

• How to Form S-Corp in Florida 2026: Complete Step-by-Step Guide
• How to Form S-Corp in New Jersey: 2026 Step-by-Step Guide
• How to Form S-Corp in New York: 2026 Step-by-Step Guide
• How to Form S-Corp in Rhode Island: 2026 Step-by-Step Guide
• How to Form Corporation in Illinois: 2026 Step-by-Step Guide

FAQ

How long does it take to form an S-Corp in Illinois?

The Illinois Secretary of State processes Articles of Incorporation in 5-10 business days for standard filings as of April 2026. Expedited processing may be available for additional fees. The S-Corp election with the IRS is processed separately and can take several weeks.

Can I be my own registered agent in Illinois?

Yes, you can serve as your own registered agent if you’re an Illinois resident with a physical address in the state. However, your name and address will be public record, and you must be available during business hours to accept legal documents.

What’s the difference between forming a corporation and an S-Corp in Illinois?

An S-Corporation is a tax election, not a separate entity type. You first form a regular corporation with Illinois, then elect S-Corp tax status with the IRS by filing Form 2553. The state formation process is identical.

Do I need an attorney to form an S-Corp in Illinois?

While not legally required, consulting an attorney is advisable for complex situations. The formation process itself is straightforward, but S-Corp tax elections and ongoing compliance can be complex.

Can a single person form an S-Corp in Illinois?

Yes, Illinois allows single-shareholder S-Corporations. However, you’ll still need at least one director and must follow all corporate formalities to maintain limited liability protection.

What happens if I miss the annual report deadline?

Illinois charges late fees for overdue annual reports and may administratively dissolve corporations that fail to file. Dissolved corporations can typically be reinstated by filing required reports and paying penalties.

Are there restrictions on S-Corp shareholders?

Yes, S-Corps are limited to 100 shareholders, cannot have corporate or partnership shareholders, and can only issue one class of stock. All shareholders must be U.S. citizens or residents.

How much does it cost to maintain an S-Corp in Illinois annually?

The minimum annual cost includes the $75 annual report fee to Illinois. Additional costs may include registered agent fees ($100-300), tax preparation, and maintaining corporate records. Total annual costs typically range from $200-800 depending on your service needs.

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This article is for informational purposes only and should not be considered legal or tax advice. Consult with a qualified attorney or accountant for guidance specific to your business situation.