Illinois Estate Tax Calculator 2026
Illinois taxes estates above a $4,000,000 exclusion — far below the $15 million federal exemption — using an interrelated calculation administered by the Illinois Attorney General. Enter the taxable estate value to estimate the Illinois estate tax, including apportionment for estates with property outside Illinois. Runs entirely in your browser.
2026 Illinois figures used: $4,000,000 exclusion per decedent (unchanged since 2010, not inflation-adjusted, no spousal portability). Tax computed with the Illinois Attorney General's interrelated calculation on the pre-2002 federal state death tax credit framework. Verified against the AG's published example: a $5,000,000 all-Illinois estate owes $285,714.
Frequently Asked Questions
What is the Illinois estate tax exemption for 2026?
$4,000,000 per person. It has been stuck at $4 million since 2010 with no inflation adjustment, while the federal exemption rose to $15 million per person in 2026. That gap means many Illinois estates owe state estate tax with zero federal estate tax. Illinois also has no spousal portability — a married couple can't combine their two $4M exclusions without a credit shelter trust.
How is Illinois estate tax calculated?
Illinois uses the pre-2002 federal state death tax credit rate table (graduated 0.8%–16%) with a $4 million exclusion, computed through an interrelated calculation — the Illinois tax is deductible from the estate it applies to, which feeds back into the math. The Illinois Attorney General publishes the worked method: a $5,000,000 all-Illinois estate owes $285,714. This calculator reproduces that calculation.
Does Illinois have an inheritance tax or gift tax?
No inheritance tax — beneficiaries owe nothing to Illinois on what they inherit. There is no standalone Illinois gift tax, but adjusted taxable lifetime gifts count toward the $4 million filing threshold: if gross estate plus taxable gifts exceeds $4M, an Illinois Form 700 must be filed even if no federal return is required.
I'm not an Illinois resident. Do I owe Illinois estate tax?
Possibly, on Illinois-situs property (real estate and tangible personal property in Illinois). The executor first computes the tax as if all assets were in Illinois, then apportions it by the ratio of Illinois assets to total assets — enter that percentage above. A nonresident return uses the Form 700 Addendum.
What about the federal estate tax?
For 2026 the federal exemption is $15,000,000 per person ($30M for married couples), so only estates above that owe federal tax at 40%. An Illinois estate between $4M and $15M typically owes Illinois tax but no federal tax — the exact situation this calculator is for.
When is the Illinois estate tax return due?
Illinois Form 700 is generally due 9 months after the date of death, filed with the Illinois Attorney General (not the Department of Revenue). Extensions are available, but interest may accrue on unpaid tax.
How accurate is this estimate?
It's a planning estimate, not a tax return. Real Illinois estate tax depends on allowable deductions (marital, charitable, debts, administration expenses), QTIP elections, and the Attorney General's official interrelated computation. For estates near or above $4M, work with an Illinois estate attorney — and confirm with the AG's official estate tax calculator before filing.