Illinois PTET Election: 4 Essential Rules on PPRT, Estimates, and Credits

Illinois is one of the more nuanced states to navigate when a pass-through entity weighs the elective PTE tax. Two taxes run side by side on your client's entity: the 4.95% PTE tax and the personal property replacement tax. The estimated payment base combines both, the credit on partner returns is calculated separately from the credit in neighboring states, and the election was permanent only after December 2025 legislation. At BusAcTa Advisors, we see Illinois PTET election returns handled incorrectly by out-of-state preparers who treat Illinois like New York or New Jersey. It isn't. This guide walks through the four rules that matter most for any preparer or firm handling Illinois pass-through entities.

This is general information, not tax advice. Consult a qualified tax professional for advice specific to your clients' situations.

Rule 1: The Illinois PTET Election Is Now Permanent, at 4.95%

The Illinois PTET election was originally scheduled to sunset for tax years beginning on or after January 1, 2026. Governor Pritzker signed SB 1911 on December 12, 2025, removing the sunset provision and making the election permanent. Your firm can now treat the Illinois PTE tax as an ongoing planning tool, not a one-year-at-a-time decision.

The mechanics are straightforward for your client to understand. Partnerships (excluding publicly traded partnerships) and S corporations can elect annually to pay Illinois income tax at the entity level. The rate is 4.95% on the entity's calculated net income for the taxable year, matching the same rate that applies to individuals under the Illinois flat income tax. The election must be made by the due date or the extended due date of the return for that year. Once your client makes the election, it's irrevocable after the extended due date.

The Illinois PTET election is now permanent after SB 1911 was signed December 12, 2025, removing the January 1, 2026 sunset date, so your firm can plan the election as a standing annual decision.

Who benefits most from your clients making this election? Partners and shareholders whose MAGI exceeds approximately $505,000 in 2026 face a federal SALT cap that phases back toward $10,000, so the entity-level deduction remains their only path to a full state tax deduction. Partners below that threshold should model whether the OBBBA's expanded $40,400 individual cap in 2026 already covers their Illinois income tax before you recommend the election. For high-income partners, the election still wins. For moderate-income partners, the math changed after OBBBA and deserves a fresh look each year.

Rule 2: The PTET Stacks on Top of the Replacement Tax, It Does Not Replace It

The personal property replacement tax (PPRT) is the piece that most preparers from other states miss. Illinois imposes replacement tax on pass-through entities separately from the PTE tax, and the election does not eliminate it. Both taxes apply to your client's entity in the same year if the entity makes the PTET election.

The PPRT rates are:

• Partnerships and trusts: 2.5% of net income

• S corporations: 1.5% of net income

The PTE tax is 4.95%. An electing partnership therefore pays 2.5% replacement tax plus 4.95% PTE tax on the same base, for a combined entity-level rate of 7.45%. An electing S corporation pays 1.5% plus 4.95%, a combined rate of 6.45%. Neither rate matches anything in the other 30-plus PTET states, which is why applying a standard PTET model from New Jersey or Georgia to your Illinois client's return produces incorrect results.

An electing Illinois partnership faces a 7.45% combined entity-level rate: 4.95% PTE tax plus 2.5% replacement tax on the same net income base, so your client's total Illinois entity tax is higher than in most other PTET states.

One important interaction: the PPRT deducted on the federal return must be added back to arrive at the Illinois unmodified base income before computing the PTE tax. If your preparer runs the tax software without entering that addback manually, the Illinois PTE tax computes on a reduced base and the return understates the entity's Illinois income tax. This is a common error on returns that haven't been configured for Illinois-specific adjustments. The IDOR Publication 129 covers this interaction in detail.

Rule 3: Estimated Payments Use a Combined Base, on IDOR's 4-Quarter Schedule

Illinois estimated payments for electing entities are calculated on the combined PTE tax plus replacement tax liability, not on PTE tax alone. The IDOR is explicit: the base for computing your client's quarterly estimated payments is the sum of PTE tax and replacement tax for the year. Treating estimated payments as if they cover only the 4.95% PTE tax will produce an underpayment penalty.

The quarterly due dates are the 15th day of the 4th, 6th, 9th, and 12th months of your client's tax year. For calendar-year entities, that means April 15, June 15, September 15, and December 15. If a due date falls on a weekend or holiday, your client's payment moves to the next business day.

What is your client's required annual payment? The standard safe harbor requires the entity to pay the lesser of:

• 90% of the current year's combined PTE tax and replacement tax liability, or

• 100% of the prior year's combined liability

Pass-through entities that did not elect to pay PTE tax in their prior year have no prior-year PTE tax liability to use as your safe harbor base. They must estimate based on 90% of the current year's expected liability. That's a harder target to hit during year one of an election, so model your client's estimated payments conservatively in the first year.

If your client's income is uneven across the year, the annualized income installment method is available on Form IL-2220. The annualized method recalculates the required installment for each quarter based on actual income earned through that period, which can reduce or eliminate underpayment penalties when income is back-loaded. Step 6 of Form IL-2220 walks through the annualized computation. You can find the current form and instructions on the IDOR estimated payments page.

One more offset worth knowing: pass-through withholding credits reported on Schedule K-1-P or K-1-T that your client expects to receive can reduce the entity's estimated payment for the quarter in which that tax year falls, and can carry forward to reduce subsequent payments until used up. Entities with upper-tier pass-through income flowing in from another electing entity should factor those credits into the payment calculation rather than leaving money tied up in an overpayment.

Rule 4: The IL PTE Credit Flows Through Schedule K-1-P, Not as a Simple Proportionate Reduction

Partners and shareholders of an electing entity receive a credit against their Illinois individual income tax equal to their distributive share of the entity's PTE tax. The credit is 4.95% times the partner's share of the entity's net income. It does not include the replacement tax, only the PTE tax component.

The credit flows through on Schedule K-1-P, line 53a. From there it carries to Form IL-1040, line 28 on your client's individual return, where they claim it as a refundable credit. The credit is refundable, meaning it can generate a refund if it exceeds the partner's Illinois income tax liability.

For nonresident partners, the credit mechanics are particularly useful. A nonresident individual member of an entity that elected to pay PTE tax is not required to file Form IL-1040 for that year if the entity's credit covers the nonresident's entire Illinois income tax liability and all the nonresident's Illinois-source income comes from that entity. This exception can eliminate the requirement for nonresident owners to file Illinois individual returns, which simplifies compliance when your client's entity has many small nonresident partners.

What about tiered structures in your client's ownership chain? A pass-through entity that is itself a member of another electing entity may receive a K-1-P credit from the upper-tier entity. That credit can offset the lower-tier entity's own PTE tax liability, but your client's lower-tier entity must still pay pass-through withholding on behalf of its own nonresident members unless it also makes the PTE election. The two regimes, PTE tax and pass-through withholding, are mutually exclusive. An entity pays one or the other, not both.

What the Combined Math Looks Like in Practice

Take your client's Illinois S corporation with $1,000,000 of net income allocated entirely to two equal resident shareholders. The entity makes the PTET election for the year. Here is how the entity-level tax breaks down:

Each shareholder's share of PTE tax is $24,750. That amount appears on their Schedule K-1-P at line 53a and flows to their Form IL-1040 as a refundable credit against their Illinois income tax. The replacement tax does not generate a credit. It is an entity-level cost that reduces federal taxable income at the entity level but does not pass through as a credit to the owners.

For estimated payments, your client must cover 90% of the combined $64,500 in the current year, or $58,050, spread across four installments of roughly $14,513 each. Each installment covers both the PTE tax and the replacement tax portion, computed as a single combined liability.

The replacement tax is an entity-level cost with no credit pass-through to your client's owners. Only the 4.95% PTE tax generates the refundable credit on Schedule K-1-P.

Illinois PTET Requires Its Own Model, Not a Copied One

The Illinois PTET election is now permanent, but that doesn't make it simpler for your firm. The PPRT interaction, the combined estimated payment base, the addback required on your client's Illinois return, and the credit mechanics on their partner returns all differ from the frameworks your firm uses for New York, New Jersey, or Georgia. Getting any one of these wrong on your client's return produces an incorrect filing or an underpayment penalty. Treat Illinois as its own return type, build your client-specific checklist to match, and verify the PPRT addback is configured in your tax software before the return leaves your desk.

If your firm handles Illinois pass-through entities and needs additional tax preparation capacity during peak season, reach out to BusAcTa Advisors to discuss how our offshore tax preparation team supports CPA firms on Illinois LLC and partnership returns. You can also explore our LLC and partnership tax services for more on the return types we handle.