Illinois Estate Tax: How the $4 Million Exemption Works

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Published: October 19, 2026

Disclaimer: General information only, not tax or legal advice. Illinois rules can change, so confirm with the Attorney General or an estate attorney.

The Illinois estate tax applies when someone dies with a gross estate, plus certain lifetime gifts, worth more than $4 million, and that line still holds for 2026 deaths. Compare that with the $15 million federal exemption and you can see the problem: many Illinois families who will never owe the IRS anything can still owe the state. The tax also doesn’t ease in. Once an estate crosses $4 million, roughly 28.6 cents of each extra dollar goes to Illinois until the estate reaches about $5.36 million. A paid-off home in Naperville, two retirement accounts and a life insurance policy can get you there quicker than you’d think. This guide covers how the exemption works, what the tax costs at different estate sizes, who must file, and the planning moves that protect your heirs.

What is the Illinois estate tax?

The Illinois estate tax is a state tax on the transfer of a person’s property at death. The estate pays it before heirs receive their share, and it’s administered by the Illinois Attorney General’s Office, not the Illinois Department of Revenue.

Illinois is one of a small group of states that still charges its own estate tax on top of the federal one. The tax applies to:

• Illinois residents, on their worldwide assets (with a reduction for property located in other states).
• Nonresidents who own Illinois real estate or tangible property here, such as a Florida retiree who kept a condo in Chicago.

Everything the person owned or controlled at death goes into the gross estate: the home, bank and brokerage accounts, 401(k)s and IRAs, business interests, vehicles, and the full death benefit of any life insurance policy the person owned. If you’ve been weighing a Roth IRA vs 401k for retirement, it’s worth knowing that both count in full here. Foreign accounts count too, the same ones you’d list on an FBAR or FATCA filing.

How does the $4 million Illinois estate tax exemption work?

The exemption, which the statute calls the “exclusion amount,” is $4 million per person. Illinois treats it as a taxable threshold, not as a credit that wipes out the first chunk of tax. That small distinction is what creates the so-called cliff.

Three features make the Illinois estate tax exemption harsher than the federal version:

1. It isn’t indexed for inflation. The federal exemption climbs most years. Illinois has sat at $4 million since 2013, so every year of rising home prices and stock gains pulls more families over the line.
2. It isn’t portable. A surviving spouse can’t pick up the unused Illinois exemption of the spouse who died first. The Attorney General’s instructions say plainly that federal portability “is inapplicable” to the Illinois tax.
3. Lifetime gifts get added back. For the filing test, Illinois adds adjusted taxable gifts (gifts above the annual exclusion) to the gross estate.

What is the Illinois estate tax cliff?

You’ll see the “cliff” described in two different ways online, and only one of them is accurate.

The myth is that $1 over $4 million makes the entire estate taxable at once, producing a huge bill. The Attorney General’s own fact sheet disproves that: an estate worth $4,000,100 owes $28.

The reality is a steep ramp. Illinois figures the tax on the whole estate using an old federal credit table, but caps it at 40% of the amount above $4 million, after deducting the Illinois tax itself. Work through that circular math and the result is about 28.6% of every dollar over the threshold. A $4.1 million estate owes about $28,571. A $4.5 million estate owes about $142,857. That’s a far higher rate than the “0.8% to 16%” range most articles quote, and it lasts until the estate reaches roughly $5.36 million, where the regular table takes over.

So the real danger zone is between $4 million and about $5.4 million. Every $100,000 you move out of the estate in that band saves heirs roughly $28,600.

What is the Illinois estate tax rate?

The Illinois estate tax rate runs from 0.8% to 16% on paper, because it’s based on the pre-2002 federal state death tax credit table. In practice, the effective rate on a whole estate lands somewhere between under 1% and about 12% for most families, with the 28.6% ramp sitting just above the exemption.

Here’s what the tax looks like at common estate sizes. These figures assume a taxable estate made up entirely of Illinois property, no prior taxable gifts, and no marital or charitable deduction. They were calculated with the Attorney General’s interrelated method and match the official examples at $4,000,100 and $5 million.

Is there an Illinois estate tax calculator?

Yes. The Attorney General publishes a free “2013-2026 Decedents Estate Tax Calculator” on its estate tax page. You enter two lines from Form 700 (the taxable estate figure and the deductions figure), and it runs the interrelated calculation for you. It won’t produce a number unless both fields are filled in, which trips people up on the first try.

How does the Illinois estate tax compare to the federal estate tax?

The gap between the two is huge in 2026. According to the IRS, the federal basic exclusion rose to $15 million per person for 2026 after the July 2025 tax law (Public Law 119-21). Illinois stayed at $4 million.

That means an Illinois estate between $4 million and $15 million can owe state tax and nothing federally. A $6 million estate is the classic example: zero to the IRS, roughly $456,000 to Illinois. For a broader look at how the two systems developed, the estate tax in the United States overview on Wikipedia is a decent starting point.

Does Illinois have an inheritance tax?

No, not for anyone who died after 1982. Illinois repealed its old inheritance tax, and the Attorney General only issues inheritance tax releases for deaths before January 1, 1983. Today the estate pays the Illinois estate tax, and heirs don’t pay a separate state tax just for receiving property.

Two things still catch heirs off guard. Money pulled from an inherited traditional IRA or 401(k) is taxable income to the beneficiary. And a handful of other states (Pennsylvania, New Jersey, Kentucky, Maryland and Nebraska) still charge inheritance tax, so if the person who died lived in one of them or owned property there, that state’s rules can apply.

Who has to file an Illinois estate tax return?

An Illinois Form 700 must be filed when the gross estate, plus adjusted taxable gifts, is more than $4 million. That’s true whether or not a federal return is required. The filing test uses gross value, so an estate can be required to file even if a marital deduction brings the tax down to zero.

When is the Illinois estate tax due?

The return and the payment are both due nine months after the date of death. Here’s how the process runs:

1. Value the estate as of the date of death. Appraisals for real estate and business interests, statements for accounts.
2. Prepare Form 700 along with a federal Form 706 and its schedules, appraisals, the will and any trusts. If no federal return is needed, the Attorney General accepts the same information in another format.
3. File the original return with the Attorney General. Estates in Cook, DuPage, Lake and McHenry counties file in Chicago (115 S. LaSalle St.). All other counties file in Springfield (500 South Second Street).
4. Pay the Illinois State Treasurer, not the Attorney General, using the Treasurer’s estate tax payment form.
5. Request an extension if needed with Form 700-EXT within the nine months. The Attorney General also honors federal extensions, and if the federal tax is paid in installments, the Illinois tax can be too.

Interest and penalties are paid to the Treasurer as well, so late filing costs real money.

How are nonresidents with Illinois property taxed?

Nonresidents figure the tax as if all their assets were in Illinois, then multiply by the share of assets located here. The Attorney General’s example: a $5 million estate with half its assets in Illinois owes $142,857, exactly half of the $285,714 a fully Illinois estate would owe. Nonresidents and residents with out-of-state property both file the Form 700 Addendum.

How can you avoid or reduce Illinois estate tax?

You can’t make the tax disappear for every estate, but the common strategies work well, especially for estates in that $4 million to $5.4 million danger zone where each dollar removed saves about 28.6 cents.

Use a credit shelter trust if you’re married

This is the big one for couples. Because Illinois has no portability, leaving everything outright to a spouse wastes the first spouse’s $4 million exemption. Take a couple worth $8 million. If everything passes to the survivor, the survivor’s estate could owe about $680,634 at the second death. If the first spouse’s will or living trust puts $4 million into a credit shelter (bypass) trust, each exemption gets used and the Illinois bill can drop to zero.

Make the Illinois QTIP election

For deaths on or after January 1, 2009, an estate can make a separate Illinois QTIP election, different from the federal one. It lets the executor shelter assets from Illinois tax at the first death while still using the full federal exemption. The Attorney General’s own example shows a $13.61 million estate with a $9.61 million Illinois QTIP election owing $0 in Illinois tax. This needs a timely filed return and the surviving spouse’s details, so it’s an attorney job.

Give during your lifetime

Illinois has no gift tax. In 2026 you can give up to $19,000 per recipient per year (a married couple can give $38,000 together), and gifts within that annual exclusion don’t count back toward the Illinois threshold. Larger gifts do get added back for the Illinois calculation, but they still move future growth out of the estate. Paying tuition or medical bills directly to the school or provider doesn’t count against the annual limit at all.

Move life insurance into an ILIT

Life insurance is the asset that most often pushes Illinois families over $4 million. Transferring the policy to an irrevocable life insurance trust (ILIT) takes the death benefit out of the estate. Under federal rules the transfer has to happen more than three years before death, so this works best done early.

Leave something to charity

Charitable bequests are fully deductible. If you were already planning to give to a church, school or nonprofit, routing that gift through the will or a charitable remainder trust can pull the estate back below the line.

Is the Illinois estate tax changing in 2026?

Not yet. Lawmakers have filed bills to raise the exemption. HB2601 would double it to $8 million for deaths on or after January 1, 2026, and a separate family farm proposal (HB2677 and SB1688) would create a $6 million exemption for qualifying farms. As of this writing, the Attorney General’s current instructions for 2023 to 2026 deaths still use the $4 million exclusion. Planning around a bill that hasn’t passed is risky, so build your plan on the current $4 million number and treat any increase as a bonus. We’ll update this guide on Da Finance Blog if the law changes, but always confirm with the Attorney General before filing.

Conclusion

The Illinois estate tax kicks in above $4 million, a number that hasn’t moved since 2013 while the federal exemption climbed to $15 million. The part most people miss is the ramp right above the line, where about 28.6% of every dollar between $4 million and roughly $5.36 million goes to the state. Married couples face an extra trap because the exemption isn’t portable, so a plan that leaves everything to the surviving spouse can waste $4 million of protection. If your home, retirement accounts and life insurance add up to anywhere near that range, a credit shelter trust, an Illinois QTIP election, annual gifts or an ILIT can save your heirs tens or hundreds of thousands of dollars. Run your numbers through the Attorney General’s calculator, then talk to an Illinois estate planning attorney while there’s still time.