LLC taxed as S corp vs S corporation in Illinois: which costs less (2026)

At $100,000 profit in Illinois, an LLC taxed as an S corp costs $22,785 a year in tax and fees and an S corporation costs $22,785. On these figures an S corporation does not cost less at any profit up to $500,000.

+$0 a year

more for an S corporation than an LLC taxed as an S corp in Illinois, at these numbers.

With these settings the switch does not pay at any profit from $10,000 to $500,000. As an S corporation this uses the state's pass-through entity tax election, which lowers the cost here.

Illinois, 2026: $100,000 profit, single filer

Item	LLC as S corp	S corp	Change
Annual Report (Form BCA 14.05)ilsos.gov, checked Oct 24, 2026	$75	$75	$0
Payroll tax on your salaryirs.gov, 2026 rates	$6,639	$6,639	$0
Payroll service and tax return (estimate)	$1,800	$1,800	$0
Illinois personal property replacement income tax (partnerships and S corps)tax.illinois.gov, checked Oct 24, 2026	$819	$819	$0
Illinois pass-through entity tax, paid by the company (elected)tax.illinois.gov, checked Oct 24, 2026	$2,659	$2,659	$0
Federal income taxirs.gov, 2026 rates	$8,958	$8,958	$0
State income tax, after the PTET credittax.illinois.gov, checked Oct 24, 2026	$1,835	$1,835	$0
Yearly cost	$22,785	$22,785	+$0

What these figures count

State income tax, and state taxes on the business itself: franchise, LLC, S corp, gross receipts and excise taxes.
Social Security and Medicare on both sides of an owner salary, federal unemployment tax and the state's new-employer rate.
The 20% qualified business income deduction with its income limits and the professional-service rule.
Yearly report fees, and a cost you can change for payroll and the business tax return.

Many S corp calculators leave out state taxes and the QBI deduction, which can make the election look better than it is.

Yearly cost at each profit level

Profit	LLC as S corp	S corp	Difference
$30,000	$8,145	$8,145	+$0
$50,000	$12,097	$12,097	+$0
$75,000	$15,938	$15,938	+$0
$100,000	$22,785	$22,785	+$0
$150,000	$37,750	$37,750	+$0
$200,000	$53,532	$53,532	+$0
$300,000	$87,361	$87,361	+$0

Federal and Illinois tax and fees, single filer, revenue 1.5 times profit, default salary for S and C corps. "Difference" is S corporation minus LLC taxed as an S corp.

What the switch takes in Illinois

File the Articles of Incorporation (Form BCA 2.10) with the state: $150 (fee).
Federal return each year: Form 1120-S, due March 15, plus your own Form 1040.
State upkeep each year: Annual Report (Form BCA 14.05), $75 a year, due before the first day of the anniversary month of incorporation.

What changes between the two

Both are taxed the same way by the IRS once the election is made: salary with payroll tax, the rest as a distribution, one Form 1120-S. The difference is state law: an LLC files Articles of Organization (Form LLC-5.5) and Annual Report (Form LLC-50.1), $75 a year, a corporation files Articles of Incorporation (Form BCA 2.10) and Annual Report (Form BCA 14.05), $75 a year.

A corporation also has formalities an LLC skips: a board, bylaws, share records and yearly minutes. Most one-person businesses pick the LLC route for that reason.

Questions

How much does it save at $100,000 in Illinois?

Nothing. S corporation costs $0 a year more ($22,785 against $22,785).

Is an LLC taxed as an S corp the same as an S corp?

For federal tax, yes. For Illinois fees and paperwork, no: the LLC pays Annual Report (Form LLC-50.1), $75 a year and the corporation Annual Report (Form BCA 14.05), $75 a year.

More for Illinois

Common cases in Illinois

Other states