How Do I File Taxes for a Deceased Person in Illinois?

Illinois requires a final state income tax return for the decedent alongside the federal Form 1040; a federal estate tax return (Form 706) is required only for estates above $15,000,000.

State

Approximate Estate Value

Estate Earns Income

YesNo

Date of Death

Two returns are due.

IRS Form 1040 and IL-1040.

Federal

Final income tax return

A final federal income tax return is required for income earned from January 1 through the date of death.

Form: IRS Form 1040
Due: April 15 following year of death

Write "DECEASED," the decedent's name, and the date of death across the top of the return. If filing jointly with a surviving spouse, include both incomes. Attach Form 1310 to claim a refund, unless you are the surviving spouse filing a joint return or a court-appointed personal representative attaching a copy of the court certificate to the original return.

IRS Form 1040 File online

Illinois

Final income tax return

A final state return is required for income earned through the date of death.

Form: IL-1040
Due: April 15 following year of death (automatic 6-month extension to October 15)

Write "deceased" and date of death above taxpayer name. Attach Form IL-1310 if non-spouse claims refund. 35 ILCS 5/502.

IL-1040 File online

Tax clearance

No tax clearance is required in Illinois

Certificate of Discharge from estate tax lien available via Form 700 checkbox (handled by Attorney General). IDOR Form ITR-1 available for business tax clearance but not required for probate.

Form: Form 700 (Certificate of Discharge requested on the return)

Illinois tax clearance

Not required

Federal estate income tax return: IRS Form 1041 is only required if the estate earns $600 in gross income or more during administration.
Federal estate tax return: The estate value ($0) is below the federal exemption of $15,000,000. IRS Form 706 is generally not required.
Illinois estate income tax return: A fiduciary return is only required if the estate earns income above the filing threshold (Required if estate has IL-source net income/loss, is an IL resident filing federal Form 1041, or is a nonresident with IL-source income — 35 ILCS 5/502).
Illinois estate tax return: The estate value ($0) is below Illinois's $4,000,000 filing threshold. Illinois's filing test uses the gross estate plus lifetime taxable gifts. Note: the threshold is a cliff — once crossed, tax is computed on the entire taxable estate, not only the excess.

General information about tax filing requirements after a death, not tax or legal advice. Consult a licensed tax professional for tax questions. Data verified Sep 15, 2026

At minimum, a final federal income tax return (Form 1040) for income earned through the date of death, and Illinois requires a final state income tax return (IL-1040) as well. If the estate earns income during administration, a federal fiduciary return (Form 1041) and an Illinois fiduciary return (IL-1041) may also be required. An Illinois estate tax return must also be filed when the federal gross estate plus lifetime taxable gifts exceeds $4,000,000, a test on the gross estate that can be met even where deductions mean no tax is due.

The final federal income tax return is due April 15 following year of death. The final Illinois return is due April 15 following year of death (automatic 6-month extension to October 15). The Illinois fiduciary return is due April 15 (calendar year); automatic 6-month extension. The Illinois estate tax return (Form 700) is due 9 months after date of death.

No. Certificate of Discharge from estate tax lien available via Form 700 checkbox (handled by Attorney General). IDOR Form ITR-1 available for business tax clearance but not required for probate. Every tax obligation is still settled before the final distribution.

Yes. Illinois imposes a state estate tax on an estate above $4,000,000. The $4,000,000 threshold is a cliff: once an estate crosses it, Illinois computes tax on the entire taxable estate, not only the amount above the threshold. It is separate from the federal estate tax. A state estate tax return must be filed when the federal gross estate plus lifetime taxable gifts exceeds $4,000,000, even if no federal estate tax is owed.

Yes. Estate size does not change the final income tax return: a final Form 1040 is filed whatever the estate is worth if the decedent had income. What a smaller estate avoids is the federal estate tax return (Form 706), due 9 months after date of death (6-month extension available) and required only above $15,000,000 and the Illinois estate tax return (required when the federal gross estate plus lifetime taxable gifts exceeds $4,000,000).

Tax Filing After Death in Illinois

After a death in Illinois, both federal and state tax returns must be filed. A final income tax return covers the deceased's income through the date of death, and a separate fiduciary return may be needed if the estate earns income during administration. A federal estate tax return (Form 706) is required only for estates above the federal exemption of $15,000,000.

Illinois imposes a state estate tax on estates exceeding $4,000,000, and the return-filing test is broader than the exemption — it runs on the federal gross estate plus lifetime taxable gifts, so some estates file even though no tax is due. The $4,000,000 threshold is a cliff: once an estate crosses it, Illinois computes tax on the entire taxable estate, not only the amount above the threshold. The Illinois death tax calculator estimates the liability.

Filing deadlines depend on the type of return. The final Illinois income tax return is due April 15 following year of death (automatic 6-month extension to October 15). The state estate tax return (Form 700) is due 9 months after date of death. The Illinois estate settlement plan tracks all deadlines in order.

SimplyTrust Editorial·Updated September 20, 2026

Legal Sources

26 USC 2001(c), 2010; P.L. 119-21 §70106
26 USC 6012(b)(1)
26 USC 6018; 26 USC 6075(a)
35 ILCS 405/2
35 ILCS 5/201
35 ILCS 5/502; 35 ILCS 405/1 et seq.

Data sourced from Illinois statutes and official state code. How we research.

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