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Illinois Estate Tax Calculator: the facts

2026 law · reviewed September 3, 2026

  1. Illinois taxes estates above $4,000,000. The federal estate tax begins at $15,000,000 for deaths in 2026. Between those two lines, Illinois is the only estate tax that applies.
  2. A $5,000,000 all-Illinois estate owes the state $285,714 and the federal government $0. That is the state's own published example.
  3. Just over the line, each added dollar costs about 28.6 cents of Illinois tax. The ramp eases at about $5.4 million, where the state's credit schedule takes over.
  4. Illinois lets a surviving spouse inherit none of a late spouse's unused exclusion. A married couple with $7,000,000 owes Illinois $565,603 at the second death if everything passed outright to the survivor, and $0 if the first death set $4,000,000 aside.
  5. For an Illinois decedent with one federal exclusion, the federal tax stays at $0 until the estate reaches about $16.9 million, because the Illinois tax is deducted before the federal tax is figured.
  6. Property sited outside Illinois shrinks the bill in proportion. A $5,000,000 estate with half its property in Florida owes $142,857, half the all-Illinois figure, even though Florida has no estate tax.
  7. SB 3847 would raise the line to $8,000,000 for deaths from January 1, 2027. As of September 3, 2026: Referred to Senate Assignments on February 6, 2026; a co-sponsor was added June 26, 2026. It has not passed either chamber and is not law.