If in any action there are persons interested therein whose names are unknown, it shall be lawful to make them parties to the action by the name and description of unknown owners, or unknown heirs or legatees of any deceased person, who may have been interested in the subject matter of the action previous to his or her death; but an affidavit shall be filed by the party desiring to make those persons parties stating that their names are unknown. Process may then issue and publication may be had against those persons by the name and description so given, and judgments entered in respect to them shall be of the same effect as though they had been designated by their proper names. If there has been a person who may have been interested in the action, and upon diligent inquiry it cannot be ascertained whether the person is living or dead, it shall be lawful to make those persons who would be his or her heirs and legatees parties defendant as unknown owners, the same as if he or she were known to be dead, but in all those cases an affidavit shall be filed by the party desiring to make any unknown persons who would be the heirs or legatees of the person not known to be living or dead parties, stating that upon due and diligent inquiry it cannot be ascertained whether or not the person is living or dead and further stating that the names of the persons who would be his or her heirs or legatees are unknown. Process may then issue and publication may be had against all parties by the name and description of unknown owners, and judgments entered in respect to the unknown parties shall be of the same effect as though they had been designated by their proper names. Only one affidavit is necessary under the provisions of this section for the purpose of making persons described herein parties to the action.
2-413.Unknown parties.
Article II. Civil Practice · Part 4. Parties · Not amended since adoption on record · Last verified July 20, 2026
In one sentenceSection 2-413 lets a party bring in interested people whose names are unknown — including unknown heirs of a deceased person or of someone whose life or death can't be confirmed — by affidavit, description, and publication, with judgments binding them as if they'd been named.
Full Text of 735 ILCS 5/2-413
Plain-English Summary
If people interested in an action have names that are unknown, they can be made parties under a description — "unknown owners," or "unknown heirs or legatees" of a deceased person who had an interest in the subject matter before dying. The party wanting to add them must file an affidavit stating that their names are unknown. Process can then issue and publication can run against them under that description, and any judgment entered against them carries the same effect as if they'd been named by their real names.
The section also covers a trickier case: someone who may have had an interest in the action, where diligent inquiry can't establish whether that person is alive or dead. There, the people who would be that person's heirs or legatees can be made unknown-owner defendants just as if the person were known to be dead — but the party adding them must file an affidavit stating that diligent inquiry couldn't establish whether the person is alive or dead, and that the names of the would-be heirs or legatees are unknown. Process and publication then proceed the same way, with judgments carrying the same binding effect.
Only one affidavit is needed to bring in all the unknown persons described in the section, no matter how many there are.
Frequently Asked Questions
How does a party add someone to a case whose name is unknown?
By describing them as "unknown owners," or as the "unknown heirs or legatees" of a deceased person who had an interest in the subject matter before dying, after filing an affidavit stating that their names are unknown. Process and publication then proceed against them under that description.
What happens if no one can tell whether a potentially interested person is alive or dead?
The people who would be that person's heirs or legatees can be made parties as unknown owners, the same as if the person were known to be dead, but the affidavit must state that diligent inquiry couldn't establish whether the person is living or dead and that the names of the would-be heirs or legatees are unknown.
Is a judgment against unknown parties as binding as one against a named party?
Yes. Judgments entered against unknown parties named and served under this section carry the same effect as if the parties had been designated by their proper names.
How many affidavits does a party need to file to bring in unknown persons?
Only one, regardless of how many unknown persons are being added under this section.
What must the affidavit for unknown parties say?
At minimum, that the names of the persons being added are unknown. Where the question is whether a potentially interested person is alive or dead, the affidavit must also state that diligent inquiry couldn't resolve that and that the names of the would-be heirs or legatees are unknown.
Amendment History
(Source: P.A. 83-707.)
Source & verification. Section text and amendment history are
reproduced verbatim from the Illinois Compiled Statutes, published by the
Illinois Compiled Statutes, Illinois General Assembly / Legislative Reference Bureau. Last verified July 20, 2026.
· Official source
Also known as: unknown owners lawsuit illinoisunknown heirs illinois lawsuitservice by publication unknown partiesaffidavit for unknown defendants