Where partition is sought as to all interests in the property, the plaintiff may join as defendants "all persons unknown claiming any interest in the property," naming them in that manner.
§ 872.550.Joiner of All Persons Unknown Claiming Interest
Title 10.5. Partition of Real and Personal Property · Chapter 2. Commencement of Action · Article 4. Parties · Enacted 1976 · no amendments on record · Last verified July 28, 2026
In one sentenceSection 872.550 lets the plaintiff, when seeking partition of all interests in the property, join "all persons unknown claiming any interest in the property" as defendants by that description, without having to identify them individually.
Full Text of § 872.550
Plain-English Summary
Even after using §§ 872.510, 872.520, and 872.530 to name every known or identifiable interest holder, a plaintiff can't always be certain no one else has a claim. This section closes that gap. When the plaintiff seeks partition of all interests in the property, the complaint may join "all persons unknown claiming any interest in the property" as defendants, using exactly that descriptive language instead of individual names.
Because these defendants are unknown by definition, service on them proceeds by publication under § 872.310(b), following the additional procedures in §§ 872.320 and 872.330. This joinder device is what makes it possible for a partition judgment to bind literally everyone with a stake in the property, known or not, when that's what the plaintiff is seeking.
Frequently Asked Questions
How does a plaintiff cover unidentified interest holders in a partition action?
By joining "all persons unknown claiming any interest in the property" as defendants, described in exactly that way, when partition is sought as to all interests.
How are these unknown defendants served with the lawsuit?
Can this device be used if the plaintiff only wants to partition part of the interests in the property?
The statute applies where partition is sought as to all interests in the property -- it's tied to seeking a complete resolution of everyone's rights.
Amendment History
Added by Stats. 1976, Ch. 73.
Source & verification. Section text is reproduced verbatim from
the Deering's California Codes Annotated / vLex. Enacted by the California Legislature.
Last verified July 28, 2026.
· Official source
Also known as: all persons unknown claiming interest partition californiaunknown defendants partition lawsuit