Choosing between an S-Corp and an LLC is one of the most consequential decisions an Illinois founder makes. Both limit personal liability. Both can provide pass-through taxation. But they differ in flexibility, compliance requirements, and long-term scalability—and the wrong choice can cost you in taxes, investor readiness, and administrative burden.
This guide breaks down every meaningful difference so you can make the right call for your business.
What Is an LLC?
A Limited Liability Company (LLC) is a state-created business entity that separates your personal assets from business liabilities. Illinois LLCs are governed by the Illinois Limited Liability Company Act (805 ILCS 180). Members hold ownership interests, and the company can be managed by members or designated managers.
By default, a single-member LLC is taxed as a disregarded entity (like a sole proprietorship), and a multi-member LLC is taxed as a partnership—both passing income directly to owners without entity-level federal income tax.
What Is an S-Corp?
An S-Corporation is not a separate business structure under state law—it’s a federal tax election made by filing IRS Form 2553. You first form either a corporation or an LLC under Illinois law, then elect S-Corp status with the IRS.
S-Corps pass income and losses through to shareholders, avoiding double taxation. But the IRS imposes strict eligibility rules: no more than 100 shareholders, all must be U.S. citizens or permanent residents, and only one class of stock is allowed.
S-Corp vs. LLC: Side-by-Side Comparison
| Feature | LLC | S-Corp (via LLC or Corp) |
|---|---|---|
| Formation document | Articles of Organization | Articles of Incorporation (or LLC + election) |
| Governing document | Operating Agreement | Bylaws (Corp) or Operating Agreement (LLC) |
| Ownership flexibility | High — any person or entity can be a member | Limited — 100 max, U.S. persons only |
| Stock classes | N/A — flexible membership interests | One class only (no preferred stock) |
| Self-employment tax savings | Potentially none (all income is SE taxable) | Yes — only salary is subject to payroll taxes |
| Investor compatibility | VC-friendly if structured correctly | Not VC-compatible (can’t have multiple stock classes) |
| Annual compliance | Lower — annual report + minimal filings | Higher — payroll, reasonable salary requirement, W-2 filings |