LLC or S corp for a physician in Illinois (2026)

A physician in Illinois with $270,000 of profit pays $91,747 a year in tax and fees as a sole proprietor and $92,918 as an LLC taxed as an S corp, with a $189,000 salary. The S corp starts to pay at about $277,500 of profit.

+$1,171 a year

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

Switching from a sole proprietorship to an LLC taxed as an S corp starts to pay at about $277,500 of profit, with the same settings. Setting up costs $150 once in state filing fees. As an LLC taxed as an S corp this uses the state's pass-through entity tax election, which lowers the cost here.

Illinois, 2026: $270,000 profit, single filer

Item	Sole prop	LLC as S corp	Change
Self-employment taxirs.gov, 2026 rates	$30,553	$0	−$30,553
Federal income taxirs.gov, 2026 rates	$48,719	$48,845	+$126
State income tax, after the PTET credittax.illinois.gov, checked Oct 24, 2026	$12,475	$9,211	−$3,264
Annual Report (Form LLC-50.1)ilsos.gov, checked Oct 24, 2026	$0	$75	+$75
Payroll tax on your salaryirs.gov, 2026 rates	$0	$28,878	+$28,878
Payroll service and tax return (estimate)	$0	$1,800	+$1,800
Illinois personal property replacement income tax (partnerships and S corps)tax.illinois.gov, checked Oct 24, 2026	$0	$968	+$968
Illinois pass-through entity tax, paid by the company (elected)tax.illinois.gov, checked Oct 24, 2026	$0	$3,141	+$3,141
Yearly cost	$91,747	$92,918	+$1,171

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.

At three profit levels

Profit	Salary used	Sole prop	LLC	LLC as S corp	C corp
$180,000	$126,000	$55,194	$56,954	$56,959	$64,801
$270,000	$189,000	$91,747	$93,362	$92,918	$103,053
$390,000	$244,000	$146,119	$149,603	$143,564	$152,556

Salary is the BLS median for the job ($244,180), capped at 70% of profit. Revenue 2 times profit. Single filer.

What matters for physicians

The IRS treats this work as a specified service trade or business, so the 20% QBI deduction phases out above $201,750 of taxable income (single). Health is a specified service under Treas. Reg. 1.199A-5(b)(2)(ii), which covers medical services by physicians, nurses, dentists and similar practitioners. law.cornell.edu
Pay figure is for family medicine physicians, the largest group with a published median. Many states make licensed professionals use a professional LLC or professional corporation, and California does not let an LLC render services that need a state license, so check the state board before forming. leginfo.legislature.ca.gov
An S corp here adds Illinois personal property replacement income tax (partnerships and S corps).

What the switch takes in Illinois

File the Articles of Organization (Form LLC-5.5) with the state: $150 (fee).
Get an EIN from the IRS (free, online) and open a business bank account in the new name.
Check the business can elect: no more than 100 shareholders, all of them US citizens or residents (no nonresident alien owners), and one class of stock. IRS
File IRS Form 2553 to elect S corp tax treatment, within 2 months and 15 days of the start of the tax year it should apply to. See how the S corp election works.
Register with Illinois as an employer and run payroll for your own salary: federal Forms 941 each quarter, Form 940 and a W-2 each year. New employers pay Illinois unemployment tax at 3.35% on the first $14,250 of wages. ides.illinois.gov See what payroll costs.
Federal return each year: Form 1120-S, due March 15, plus your own Form 1040.
State upkeep each year: Annual Report (Form LLC-50.1), $75 a year, due before the first day of the anniversary month of organization. New for you: Illinois personal property replacement income tax (partnerships and S corps).

Questions

Should a physician in Illinois form an S corp?

At $270,000 of profit, not on these figures: the S corp costs $1,171 a year more than staying a sole proprietor.

Is an LLC worth it for a physician in Illinois?

For tax, a single-member LLC changes nothing: $93,362 a year against $91,747, the difference being Illinois's LLC fees and LLC taxes. It separates business liability and is the base for an S corp election.

Other professions in Illinois

Other states