Illinois estate tax in 2026
Illinois taxes estates whose value, gifts included, exceeds $4,000,000, and the tax is computed with an interrelated formula published by the Attorney General. Enter the taxable estate to see the Illinois tax for a death in 2026.
- Threshold
- $4,000,000
- Tax on 5 million
- $285,714
- Spouse carryover
- none
- Form 700 due
- 9 months
Illinois estate tax for a death in 2026
$285,714
5.7 % of the taxable estate; exemption $4,000,000.
| Exemption or threshold | $4,000,000 |
| Amount above it | $1,000,000 |
| State estate tax | $285,714 |
| Return due | 9 months after death |
Estimate on the state table for 2026. Federal tax comes on top above the federal exclusion.
| Taxable estate | State tax | Share |
|---|---|---|
| $4,000,000 | $0 | 0.0 % |
| $5,000,000 | $285,714 | 5.7 % |
| $6,000,000 | $456,071 | 7.6 % |
| $7,000,000 | $565,603 | 8.1 % |
| $8,000,000 | $680,634 | 8.5 % |
| $9,000,000 | $801,049 | 8.9 % |
| $10,000,000 | $926,923 | 9.3 % |
Compiled by Radif Partners · How we calculate · figures read on the state revenue department, the statute and irs.gov · not legal or tax advice
Illinois owes no estate tax on estates of $4,000,000 or less, gross value plus adjusted taxable gifts. The Attorney General, who administers the tax, stresses that this $4,000,000 is a taxable threshold and not a credit: once it is crossed, the tax is computed on the whole estate, and it rises quickly. An estate of $5,000,000 entirely in Illinois owes $285,714, which is 28.6 % of the $1,000,000 above the threshold; the same estate with half its assets in Florida owes $142,857. The computation is interrelated because the Illinois tax reduces the estate on which it is calculated, and it uses the old federal credit table with a limit tied to a 40 % federal rate. Illinois does not apply federal portability, so a surviving spouse cannot add the first spouse's unused amount. Form 700 is filed with the Attorney General within nine months of death, with a federal Form 706 or equivalent information attached.
A threshold, not a credit
The Attorney General's fact sheet says it plainly: "The exclusion amount is a taxable threshold and not a credit against tax" (Illinois estate tax fact sheet). In a credit system such as the federal one, $4,000,000 would be tax free in every estate and only the excess would bear tax. In Illinois, an estate at $4,000,000 owes nothing, but an estate above it owes a tax measured on the whole taxable estate, held down near the threshold by a ceiling that keeps the tax below the amount by which the estate exceeds $4,000,000.
| Taxable estate, all in Illinois | Illinois tax | Tax as a share of the excess over the threshold |
|---|---|---|
| $4,000,000 | $0 | none |
| $4,500,000 | $142,857 | 28.6 % |
| $5,000,000 | $285,714 | 28.6 % |
| $6,000,000 | $456,071 | 22.8 % |
| $8,000,000 | $680,634 | 17.0 % |
| $10,000,000 | $926,923 | 15.4 % |
| $15,000,000 | $1,609,310 | 14.6 % |
Up to about $5,360,000, the tax equals 40/140 of the excess, 28.6 % of each dollar above $4,000,000. That is the ceiling at work. Beyond that size the Table B computation becomes the smaller of the two and the tax follows the old federal credit for state death taxes, whose top rate is 16 %. The federal estate tax adds nothing until the estate passes $15,000,000, so for most Illinois estates this is the only death tax.
Illinois tax on another estate
Illinois estate tax for a death in 2026
$456,071
| Exemption or threshold | $4,000,000 |
| Amount above it | $2,000,000 |
| State estate tax | $456,071 |
| Return due | 9 months after death |
How the interrelated computation works
The Attorney General publishes an online calculator for decedents from 2013 to 2026 and asks estates to enter two figures from Form 700: the taxable estate and the adjusted taxable gifts. The logic, which this site reproduces, runs in two steps. First, the Illinois tax is the credit read on Table B for an adjusted taxable estate equal to the taxable estate, less the Illinois tax itself, less $60,000; since the tax appears on both sides, it is found by repeating the computation until it stops changing. Second, the tax may not exceed what a 40 % tax on the amount above $4,000,000 would leave after deducting the Illinois tax, which gives the 40/140 ceiling. The engine of this site reproduces the examples printed in the fact sheet to the dollar, and they are run as tests.
The Attorney General's own examples
| Situation | Illinois tax |
|---|---|
| Estate of $3,000,000 | $0 |
| Estate of $3,000,100 with $1,000,000 of adjusted taxable gifts | $29 |
| Estate of $4,000,000, all in Illinois | $0 |
| Estate of $5,000,000, all in Illinois | $285,714 |
| Estate of $5,000,000, half in Illinois and half in Florida | $142,857 |
The second line shows what gifts do. They are not taxed themselves, yet they count toward the threshold: $3,000,100 plus $1,000,000 of gifts is $100 over $4,000,000, and the estate owes a small tax. A large gift made years earlier can therefore bring an estate under $4,000,000 into the tax.
Property in Illinois and elsewhere
For residents and nonresidents alike, a preliminary tax is computed as if all assets were in Illinois, then multiplied by the ratio of Illinois assets to total assets, with the Form 700 Addendum for estates below 100 % (Illinois Attorney General, estate taxes). The fact sheet notes that the Florida half of the example estate is excluded from the Illinois tax even though Florida itself imposes none. Conversely, a Florida resident with a $5,000,000 estate including a $2,500,000 Chicago property would owe Illinois $142,857 on this basis. The rules of the other states are compared on property in another state.
Spouses, QTIP and the missing portability
Property left outright to a spouse is deducted, as federally. Illinois also allows a QTIP election for Illinois purposes only, made on a timely Illinois return, separate from any federal QTIP election; the fact sheet's last example, an estate of $13,610,000 with a surviving spouse and an Illinois QTIP election of $9,610,000, owes nothing. What Illinois does not accept is portability: the note at the end of the fact sheet says that the carry-over of the unused federal exemption to the surviving spouse "is inapplicable to the computation and assessment of the Illinois Estate Tax". Couples whose combined estate exceeds $4,000,000 therefore face the question discussed on married couples.
Filing with the Attorney General
Form 700 must be filed with the Illinois Attorney General within nine months of the date of death, with the federal Form 706 and its schedules, appraisals, wills and trusts. An estate that does not need a federal return may present the same information in another format. Extensions are granted on Form 700-EXT or another written request, and the Attorney General recognizes federal extensions.