The Illinois estate tax, computed honestly.
Illinois draws its estate-tax line at $4,000,000, far below the federal $15,000,000. Enter a taxable estate to see what the two taxes would claim under 2026 law, calculated the way the state itself calculates.
- Illinois estate tax
- $456,071
- Federal estate tax
- $0
- Combined
- $456,0717.6% of the estate
Above the Illinois line, under the federal one: Illinois is the only estate tax in the room at this size.
How it counts. This tool does the math the way Illinois itself does it. The state publishes its own calculator, and ours follows that computation exactly. We checked it against the state's own worked examples, a $4,000,000 estate owing $0, a $5,000,000 estate owing $285,714, and it agrees to the dollar. For the federal number, the Illinois tax comes off the top first, and 40% applies to whatever remains above the $15,000,000 federal line under 2026 law.
What it assumes. One taxable estate, everything sitting in Illinois, nothing passing to a spouse or to charity, and the law as it stands in 2026. The federal side is yours to set: a single $15,000,000 exclusion, or $30,000,000 where a late spouse's full unused exclusion was ported; the real ported amount is whatever the first estate did not use. Real lives differ in exactly these ways, which is the point of planning: for a married couple the first death usually owes nothing at all, and these numbers describe the second. An actual filing runs through the state's calculator and Form 700, with an attorney's hands on it.
Where we fit in. We integrate tax considerations into your investment strategy and collaborate with estate attorneys and CPAs to ensure your plan is coordinated. We are not a law firm or accounting firm, so we do not provide legal or tax advice. Everything in this material is for educational purposes, based on primary sources. Before taking any action, please consult the appropriate professionals to apply these ideas to your situation.
The number is the start, not the plan.
Why the line sits at $4 million, why crossing it is a ramp and not a trapdoor, the married-couple trap that quietly wastes an exclusion, and the lawful, well-worn ways families keep from paying by accident. We wrote it up plainly:
Last reviewed June 2026. Illinois law may change: a bill pending in Springfield (SB 3847) would raise the exclusion to $8,000,000 in 2027; it is not law today, and this tool follows the law that exists. See the article's notes for citations, including the method note documenting the validation.