Illinois Estate Tax Calculator 2026
Estimate Form 700 tax using the same iterative bracket logic as the Illinois Attorney General calculator. Enter tentative taxable estate, adjusted taxable gifts, and the Illinois situs percentage for resident or nonresident apportionment.
Use 100% for an all-Illinois estate. Form 700 apportions a nonresident estate using Illinois property divided by total property.
Illinois estate tax
$285,714Pre-apportionment tax
$285,714Estate plus adjusted gifts
$5,000,000Effective rate on estate
5.71%Illinois uses an interrelated calculation: the state estate-tax deduction changes the tentative taxable estate, which changes the tax, so the official method repeats until the result changes by less than $1.
This implementation follows the Illinois Attorney General calculator's published client-side bracket table, $60,000 adjustment, federal-limit trial, and rounding. A $5,000,000 all-Illinois estate reproduces the state's published $285,714 example.
Official Form 700 inputs
Form 700 asks for the tentative taxable estate on line 3 and adjusted taxable gifts on line 4; their sum appears on line 5. The state's calculator uses lines 3 and 5. This page derives line 5 from the estate and gift inputs, then implements the official client-side bracket table and trial sequence.
For nonresident decedents, Form 700 first computes the full preliminary tax and multiplies it by Illinois-situs property divided by worldwide gross property. QTIP elections, alternate valuation, federal deductions, and asset classification can materially change the inputs, so an executor should reconcile the estimate with the return and professional advice.
Frequently asked questions
What is the Illinois estate tax threshold in 2026?
Illinois uses a $4,000,000 threshold after adjusted taxable gifts. It is a filing threshold rather than a portable federal-style exemption, and it is not indexed for inflation.
How much Illinois estate tax is due on a $5 million estate?
The Illinois Attorney General publishes an example of $285,714 for a $5 million estate with all property in Illinois and no adjusted taxable gifts. This calculator reproduces that result.
Why is Illinois estate tax an interrelated calculation?
The state estate-tax deduction reduces the tentative taxable estate, which changes the state credit-table result. The official calculator repeatedly recalculates tax until successive trials differ by less than $1, then applies a federal-limit trial when required.
Does Illinois have estate tax portability?
No. Federal DSUE portability does not transfer unused Illinois threshold to a surviving spouse. Illinois permits its own QTIP election, which can defer state tax but requires a timely Illinois return and supporting trust information.
Sources
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