Free tool · Updated for 2026 Illinois law

Illinois Estate Tax Calculator

Illinois taxes estates above a $4,000,000 exclusion equivalent — far below the federal threshold, and with no portability between spouses. Estimate your exposure below, then see what the right structure can do about it.

This is an estimate for Illinois residents with Illinois property. It doesn't account for the marital deduction, charitable gifts, out-of-state real estate, or your specific facts. Confirm with Illinois Form 700 and the Illinois Attorney General's calculator before relying on any number.

How Illinois estate tax works

Illinois has its own estate tax, separate from the federal one. When everything a person owns at death adds up to more than $4 million, the state taxes the part above that line. This tool runs the state's official formula on the value you enter and estimates what would be owed.

What catches families off guard:

The $4 million line doesn't rise with inflation, so more estates cross it every year.
Spouses can't automatically combine their two exemptions — so without planning, a couple may shelter $4 million instead of $8 million.
Only the amount over $4 million is taxed, but the rate climbs fast — from under 1% up to about 16%.
“Everything you own” is broad: your home, retirement accounts, a business, and life insurance you control all count.

The technical version: the estimate uses the pre-2001 federal “state death tax credit” table from Illinois Form 700. Because the tax is figured on the estate after the tax itself is subtracted, effective rates rise sharply just over the $4 million line.

Why Illinois estate tax catches families off guard

The federal estate tax exemption sits in the multi-millions per person, so most families assume estate tax is someone else's problem. Illinois is different. The state's $4,000,000 exclusion is not indexed for inflation, it is not portable between spouses, and a family home, retirement accounts, and a life insurance policy can add up past it quickly — especially for business owners and Metro East and St. Louis-area families whose real estate has appreciated.

Without planning, the exclusion of the first spouse to die can be lost permanently. That single oversight is one of the most expensive mistakes we see, and it is almost always avoidable.

What planning can do about it

Bypass (credit shelter) trusts

Capture both spouses' $4M exclusions instead of losing the first one — often the single largest lever for a married couple.

Lifetime gifting

Annual-exclusion gifts, valuation-discounted transfers, and 529 funding move value out of the taxable estate over time.

Irrevocable trusts

ILITs and other irrevocable structures remove appreciating assets — and life insurance proceeds — from your taxable estate.

QTIP & marital planning

Illinois QTIP elections defer tax to the second death while preserving control and flexibility. Read more →

Explore estate & gift tax planning

See what your number could be — with a plan in place

The calculator shows exposure as it stands today. A short consultation shows how much of it is reducible, and what to do first.

Schedule a consultation Contact the firm