The Illinois replacement tax (PPRT), explained

What the replacement tax is

Illinois once let local governments tax business personal property directly. The state replaced that system with a tax it collects itself and distributes to those local governments. That history is the name. The replacement tax is imposed on the net income of businesses organized as partnerships and corporations, and the Department of Revenue administers it alongside the income tax. It is not a sales tax, not a property tax bill you receive, and not optional for the entities it covers. It rides on the same net income figure the business reports for Illinois income tax purposes.

The rates

The rate depends on the entity. Partnerships pay 1.5 percent of net income. S corporations also pay 1.5 percent. C corporations pay 2.5 percent. These percentages sit on top of the other taxes the owners or the entity owe. For an S corporation, that means the shareholders pay Illinois individual income tax on their share of the income at 4.95 percent, and the corporation itself pays the 1.5 percent replacement tax on the same income. The combined weight is the number to compare when weighing an S election, and it is the part of the comparison that online calculators most often leave out, because most states have no equivalent tax.

Who does not pay it

Sole proprietors do not pay the replacement tax. There is no entity, and the tax does not reach individuals. A single-member LLC taxed as a disregarded entity does not pay it either, for the same reason: the income is treated as the owner's own, and the owner's Illinois obligation is the individual income tax. This is the quiet advantage of the default structures for a solo owner. The moment the same LLC elects to be taxed as an S corporation, or the owner forms a partnership with a second member taxed as a partnership, the replacement tax enters the picture at 1.5 percent of net income. Nothing about the work changed. The tax follows the entity classification, not the activity.

Why it surprises S-corp owners

The S-corp election is usually sold on one number: the self-employment tax it saves. An owner earning enough that salary-and-distribution splitting beats the 15.3 percent self-employment tax comes out ahead, often well ahead. Then the Illinois return adds 1.5 percent of the S corporation's net income as replacement tax, a line that did not exist when the same business was a disregarded LLC. The election usually still wins at the incomes where it makes sense. But it wins by less in Illinois than the national articles suggest, and at borderline incomes the replacement tax can be the difference between an election that pays and one that merely adds payroll paperwork. Run the Illinois numbers, not the generic ones. Our S-corp election page works through the full comparison.

The neighboring taxes, so they stop blurring together

Illinois also has a franchise tax, which applies to corporations and not to LLCs. It is a separate charge tied to corporate capital, and LLC owners can ignore it. Separately again, Illinois offers an elective pass-through entity tax at 4.95 percent, which partnerships and S corporations may choose to pay at the entity level as a workaround to the federal cap on state tax deductions. That one is optional, strategic, and frequently confused with the replacement tax because both are entity-level and both involve pass-throughs. The replacement tax is mandatory for the entities it covers. The PTE tax is a choice. Your accountant uses the second to plan around the first's neighborhood, but they are different taxes with different purposes.

The solo owner's summary

Stay a sole proprietor or a disregarded single-member LLC, and the replacement tax never touches you. Elect S-corp status or take on a partner in a partnership structure, and 1.5 percent of net income joins your Illinois tax bill. Form a C corporation and the rate is 2.5 percent. The tax is not a reason to avoid those structures. It is a line item that belongs in the math before you choose them, and in Illinois it is the line item most often missing.