🏛️ Illinois estate tax: $4M exclusion. Cliff rule — if estate exceeds $4M, the ENTIRE estate is taxable. $5M estate owes ~$285,714. $10M owes ~$926,923. No portability between spouses. Enter your estate below for exact estimate — free, no signup.
⚠️ Estimate only. Illinois uses an interrelated calculation — exact tax may vary. Consult an Illinois estate attorney.
📋 Key Takeaways — Illinois Estate Tax at a Glance
Exclusion: $4,000,000 (unchanged since 2012)
Cliff rule: $1 over $4M makes entire estate taxable
Rates: graduated, top ~16%, interrelated calculation
$5M estate → ~$285,714 tax (official example)
No portability between spouses
Administered by Illinois Attorney General, not Dept of Revenue
Form 700 due within 9 months of death
ℹ️ This free Illinois estate tax calculator uses the $4M exclusion and official 2026 published examples. Enter gross estate and deductions to estimate Illinois estate tax and amount heirs receive. Updated November 2026.
📊 Illinois Estate Tax: $4M exclusion | Cliff rule: entire estate taxable if over $4M | Top rate ~16% | No portability | Form 700 to Attorney General
💡 Pro Tip: If your estate is near $4M, consider lifetime gifting (no Illinois gift tax) or a credit shelter trust for married couples to preserve both exemptions.
📊 Illinois Estate Tax by Estate Size (Official Examples)
Gross Estate
Illinois Estate Tax
Heirs Receive
Effective Rate
$4,000,000
$0
$4,000,000
0%
$4,100,000
$28,571
$4,071,429
2.86%
$4,500,000
$142,857
$4,357,143
3.17%
$5,000,000
$285,714
$4,714,286
5.71%
$6,000,000
$456,071
$5,543,929
7.60%
$10,000,000
$926,923
$9,073,077
9.27%
Source: Official Illinois Attorney General examples for 2026 deaths, all assets in Illinois, no deductions.
📊 Illinois vs Federal Estate Tax
Feature
Illinois
Federal (2026)
Exclusion
$4,000,000
$13,990,000
Tax Structure
Cliff — entire estate taxable
Only amount above exclusion
Top Rate
~16%
40%
Portability
❌ No
✅ Yes
Calculation
Interrelated formula
Simple rate schedule
Administered by
IL Attorney General
IRS
🏛️ $5M Estate — Illinois Only
Estate: $5,000,000 | Deductions: $0
Result: IL Tax = $285,714 | Heirs = $4,714,286
✅ "Federal tax $0, but Illinois takes $285K. Planning matters."
🏛️ $10M Estate — High Tax
Estate: $10,000,000 | Deductions: $0
Result: IL Tax = $926,923 | Heirs = $9,073,077
⚠️ "Nearly $1M in Illinois tax. Credit shelter trust could save $285K."
How Much Is Illinois Estate Tax? (Quick Answer)
Formula (approximation): Illinois estate tax applies when the taxable estate exceeds $4,000,000. Due to the cliff rule, the entire estate becomes taxable — not just the excess [citation:14].
Official examples (2026 deaths, all assets in Illinois, no deductions):
$4,000,000: $0
$4,100,000: ~$28,571
$5,000,000: ~$285,714
$10,000,000: ~$926,923
What is the Illinois Estate Tax Cliff?
Illinois uses a cliff structure. If the estate exceeds $4M by even $1, the entire estate becomes taxable [citation:14]. This is fundamentally different from the federal system, which only taxes the amount above the exemption.
Example: A $4,100,000 estate owes about $28,571 in Illinois tax. A $4,000,000 estate owes $0. Being $100,000 over costs $28,571.
Why Can't I Just Multiply by 16%?
Illinois estate tax rates are graduated and the calculation uses an interrelated formula that accounts for the estate tax itself as a deduction [citation:6][citation:14]. Multiplying the excess over $4M by a flat 16% will not give an accurate result.
The official calculator is on the Illinois Attorney General's website. This tool provides an educational estimate based on official published examples.
No Portability Between Spouses
Unlike the federal estate tax, Illinois does not offer portability [citation:14]. Each spouse has a separate $4M exemption. If the first spouse dies without using their exemption, it is lost.
Married couples should consider a credit shelter trust (bypass trust) to preserve both exemptions — potentially sheltering up to $8M from Illinois estate tax.
What Counts in the Illinois Estate?
Illinois follows the federal definition of gross estate. For residents, this includes all worldwide assets [citation:14]:
Real estate (primary home, vacation homes, investment property)
Bank and investment accounts
Retirement accounts (401k, IRA)
Life insurance proceeds (policies owned by decedent)
Business interests
Lifetime gifts made within 3 years of death are added back to the Illinois estate [citation:4][citation:14].
Illinois Estate Tax vs Federal
The 2026 federal exclusion is $13.99 million per person. The Illinois exclusion is only $4 million [citation:5][citation:14].
This means many Illinois estates owe state tax but no federal tax. The "Illinois-only zone" is estates between $4M and $14M — state-level planning is where the real work happens.
When Must Form 700 Be Filed?
Illinois Form 700 must be filed within 9 months of death if the gross estate exceeds $4,000,000 after including adjusted taxable gifts [citation:5]. This applies whether or not a federal Form 706 is required.
File with the Illinois Attorney General (not the Department of Revenue). For Cook, DuPage, Lake, and McHenry counties, file in Chicago. For all other counties, file in Springfield.
Why Use Our Illinois Estate Tax Calculator?
Our free Illinois estate tax calculator uses the $4M exclusion and official published examples. It runs entirely in your browser — no data stored, no sign-up. Whether you're planning your estate or understanding a potential tax bill, this tool gives you a clear estimate in seconds.
❓ Frequently Asked Questions
What is the Illinois estate tax exclusion for 2026?
The Illinois estate tax exclusion is $4,000,000 for 2026. This has not changed since 2012. If the gross estate after deductions exceeds $4M, Illinois estate tax may be due. The federal exclusion is much higher ($13.99M+), so many Illinois estates owe state tax but no federal tax.
What is the Illinois estate tax cliff?
Illinois uses a cliff structure. If the estate exceeds $4M by even $1, the ENTIRE estate becomes taxable, not just the excess. For example, a $4,100,000 estate owes about $28,571 in Illinois tax, not $0. This is different from the federal system which only taxes the amount above the exemption.
How much is Illinois estate tax on a $5 million estate?
For a $5,000,000 Illinois estate in 2026 with no deductions, the Illinois estate tax is approximately $285,714. The heirs receive about $4,714,286 after tax. This matches the official Illinois Attorney General example.
Does Illinois have portability between spouses?
No. Unlike the federal estate tax, Illinois does not offer portability. Each spouse has a separate $4 million exemption. If the first spouse dies without using their exemption, it is lost. Married couples need a credit shelter trust to preserve both exemptions.
What is the top Illinois estate tax rate?
Illinois estate tax rates are graduated and top out at approximately 16%. However, the calculation uses an interrelated formula, not a simple flat rate. Multiplying the excess over $4M by 16% will not give an accurate result.
Who administers the Illinois estate tax?
The Illinois estate tax is administered by the Illinois Attorney General's office, not the Illinois Department of Revenue. For questions, contact the Attorney General at 217-524-5095. Form 700 is filed with the Attorney General.
When must Form 700 be filed in Illinois?
Illinois Form 700 must be filed within 9 months of the date of death if the gross estate exceeds $4,000,000 after including adjusted taxable gifts. This applies whether or not a federal Form 706 is required.
Are lifetime gifts included in the Illinois estate?
Yes. Adjusted taxable gifts made within 3 years of death are added back to the Illinois gross estate for estate tax purposes. Illinois does not have a separate gift tax, so lifetime gifting can reduce the taxable estate if done early enough.
Do nonresidents pay Illinois estate tax?
Nonresidents pay Illinois estate tax only on Illinois-based assets: real estate, tangible personal property in Illinois, and Illinois business interests. The tax is calculated on the full estate first, then apportioned by the ratio of Illinois assets to total assets.
What is the Illinois QTIP election?
The Illinois QTIP (Qualified Terminable Interest Property) election allows property passing to a surviving spouse to qualify for the Illinois marital deduction, even if the federal QTIP election is not made. It is elected on a timely filed Illinois Form 700.
Will Illinois estate tax change in 2026?
As of the search date, the $4,000,000 exclusion remains in effect for 2026. Proposed legislation (HB1733) would raise the exclusion to match federal levels starting in 2026, but it has not been enacted. The Illinois Attorney General's official calculator still uses $4M.
Does Illinois estate tax apply to retirement accounts and life insurance?
Yes. Illinois follows the federal definition of gross estate. Retirement accounts (401k, IRA) and life insurance proceeds on policies owned by the decedent are included in the Illinois gross estate. This often pushes estates closer to the $4M threshold than expected.
💡 Expert Tips for Illinois Estate Planning
Tip #1: The cliff rule is brutal. If you're near $4M, even $1 over triggers tax on the entire estate. Consider gifting or charitable deductions to stay under.
Tip #2: Married couples: use a credit shelter trust. Without it, the first spouse's $4M exemption is wasted. With it, you can shelter up to $8M.
Tip #3: Illinois has no gift tax. Lifetime gifting (up to $19,000 per recipient per year) removes assets from your estate. Start early — gifts within 3 years of death are added back.
Tip #4: Retirement accounts and life insurance count. Many families are surprised to find these push them over $4M.
Tip #5: File Form 700 within 9 months. Late filing penalties are 5% per month, up to 25%.
Tip #6: Work with an Illinois estate attorney. The interrelated calculation is complex and the cliff rule makes precision critical.
🏛️ Still Asking "How Much Is Illinois Estate Tax?"
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🛡️ CDCalculators Illinois estate tax calculator — data sources: Illinois Attorney General official examples, 35 ILCS 405, HB1733. Last updated November 12, 2026. Disclaimer: Estimate only. Illinois uses an interrelated calculation. Consult an Illinois estate attorney.