Estate tax worksheet
Illinois Estate Tax Calculator
Illinois has a $4 million filing threshold and an interrelated estate-tax calculation. Its Attorney General’s example for a $5 million estate entirely in Illinois is $285,714. Multiplying only the amount above $4 million by a flat rate does not reproduce that result.
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Calculate Illinois preliminary estate tax
Who this covers and what to enter
Use prepared Illinois tentative taxable amounts before deducting Illinois estate tax. This estimates the state calculation and your confirmed allocation; it does not prepare Form 700 or determine federal tax.
Your estimate
Needs your figuresCalculatedConfirm the amounts and allocation to calculate.
- Estimated Illinois tax after allocation
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- Preliminary tax before allocation
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Whole-dollar estimate following the Attorney General calculator’s iterative method. This amount is not combined state and federal estate tax.
Reviewed October 1, 2026. Official calculator, labeled for 2013–2026 deaths · Current Form 700 instruction sheet.
Start with the Illinois tentative taxable estate
The official calculator takes the tentative taxable estate and that amount plus adjusted taxable gifts. Those amounts come from Form 700 Schedule A or B, lines 3 and 5. This tool asks for line 3 and the gifts added to it. An estate inventory alone may not equal line 3 after deductions and state adjustments. Form 700 input lines.
How the interrelated calculation changes the result
The state computation deducts the tentative tax while recalculating the old state death-tax credit schedule. It also applies the limiting calculation using the amount above $4 million, including adjusted gifts. The result is found iteratively, rather than by assuming that a married estate has twice the threshold.
This calculator follows the two-stage numerical procedure used by the Attorney General’s tool, including its one-dollar stopping tolerance and whole-dollar display. Near a boundary, a fully converged fractional-dollar calculation can round a dollar differently. Use the official form calculation for filing. Compare the official calculator.
| Tentative estate, no adjusted gifts | All assets allocated to Illinois |
|---|---|
| $4,000,000 | $0 |
| $4,100,000 | $28,571 |
| $5,000,000 | $285,714 |
| $6,000,000 | $456,071 |
| $10,000,000 | $926,923 |
| $20,000,000 | $2,298,965 |
These are state-only estimates using the stated tentative inputs. They do not include federal tax, prior payments, interest, penalties or other credits.
Gifts can change the calculation below a $4 million estate
For a $3,000,100 tentative estate with $1 million adjusted gifts, the published instruction-sheet example is $28 of Illinois tax. The estate amount alone is therefore insufficient. Entering gifts as zero because they are no longer in the estate can understate the result. Adjusted-gift example.
Allocate only after computing the preliminary tax
The instructions first compute a tax as if all assets were in Illinois, then apply the Illinois asset ratio. For the $5 million example, a confirmed 50% allocation gives $142,857. The ratio is a tax-situs determination, not merely the percentage of accounts held at an Illinois bank. The form addendum must support it. Form 700 allocation schedule.
Filing threshold, marriage and federal tax are separate questions
Illinois filing depends on gross estate plus adjusted taxable gifts, not just the tentative taxable estate entered here. A zero estimate does not by itself settle whether a return is required. Illinois does not use federal portability for its state calculation; resolve any Illinois QTIP election before entering the tentative amount. Filing and QTIP instructions.
For 2026, the federal basic exclusion is $15 million. Federal deductions and state death-tax interactions require their own calculation, so adding an independently calculated federal amount to the number above may overstate the combined liability. 2026 Form 706 instructions.
Illinois estate tax is administered by the Attorney General. The Illinois Department of Revenue directs estate-tax questions to that office. Department of Revenue referral. For nearby jurisdictions, see Kentucky inheritance tax and the state directory.
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