(1) When the name or a part of the name of any defendant, or when any proper party defendant to an action to establish or enforce, redeem from or discharge a lien or claim to property is unknown to the plaintiff, such defendant may be designated a defendant by so much of the name as is known, or by a fictitious name, or as an unknown heir, representative, owner or person as the case may require, adding such description as may reasonably indicate the person intended. But no person whose title to or interest in land appears of record or who is in actual occupancy of land shall be proceeded against as an unknown owner.
807.12.Suing by fictitious name or as unknown; partners’ names unknown.
Ch. 807: Miscellaneous Provisions · Last amended 1975 · Last verified July 15, 2026
In one sentenceSection 807.12 lets a plaintiff sue a defendant whose name is unknown by a partial name, a fictitious name, or a description, bars that approach against a recorded or occupying landowner, and lets a partnership suit proceed in the firm’s name until the partners are known.
Full Text of Section 807.12
(2) When the name of such defendant is ascertained the process, pleadings and all proceedings may be amended by an order directing the insertion of the true name instead of the designation employed.
(3) In an action against a partnership, if the names of the partners are unknown to the plaintiff, all proceedings may be in the partnership name until the names of the partners are ascertained, whereupon the process, pleadings and all proceedings shall be amended by order directing the insertion of such names.
Plain-English Summary
Section 807.12 deals with defendants a plaintiff cannot fully identify at the time of filing. Subsection (1) lets a defendant, or a proper party defendant in an action to establish, enforce, redeem from, or discharge a lien or claim to property, be designated by so much of the name as is known, by a fictitious name, or as an unknown heir, representative, owner, or person, adding a description that reasonably indicates the person intended. That flexibility has a limit: no person whose title to or interest in land appears of record, or who is in actual occupancy of the land, may be proceeded against as an unknown owner.
Subsection (2) addresses what happens once the true name is discovered: the process, pleadings, and all proceedings may be amended by an order directing the insertion of the true name in place of the earlier designation. Subsection (3) extends a similar approach to partnerships: in an action against a partnership where the partners’ names are unknown to the plaintiff, all proceedings may go forward in the partnership’s name until those names are ascertained, at which point the process, pleadings, and proceedings are amended by order to insert them.
Frequently Asked Questions
Can I sue someone if I do not know their full name?
Yes. Subsection (1) lets the defendant be designated by so much of the name as is known, by a fictitious name, or as an unknown heir, representative, owner, or person, with a description reasonably indicating the person intended.
Is there any limit on suing someone as an “unknown owner” of land?
Yes. Subsection (1) bars proceeding against as an unknown owner anyone whose title to or interest in the land appears of record, or who is in actual occupancy of it.
What happens once I learn the true name of a defendant I sued under a fictitious designation?
Subsection (2) lets the process, pleadings, and all proceedings be amended by an order directing the insertion of the true name instead of the designation used.
Can I sue a partnership without knowing the names of the individual partners?
Yes. Subsection (3) lets proceedings go forward in the partnership’s name until the partners’ names are ascertained, at which point the process, pleadings, and proceedings are amended to insert those names.
Does this section apply to actions involving property liens or claims?
Yes. Subsection (1) covers a proper party defendant to an action to establish, enforce, redeem from, or discharge a lien or claim to property whose identity is unknown to the plaintiff.
Amendment History
History: Sup. Ct. Order, 67 Wis. 2d 585, 748 (1975).
Source & verification. Section text and official notes are
reproduced verbatim from the Wisconsin Statutes, published by the
Wisconsin Legislature (Legislative Reference Bureau). Last verified July 15, 2026.
· Official source
Also known as: wisconsin suing an unknown defendant fictitious nameunknown owner of land lawsuit wisconsinsuing a partnership unknown partners wisconsinamending a pleading with the true name of a defendant wisconsin