Title IV: Parties · Last amended July 1, 2016 · Last verified July 14, 2026
In one sentenceRule 19 requires the court to bring in every person needed for a complete and fair resolution of a case when that's feasible, and to weigh whether the lawsuit can continue without them when it isn't.
(1)Required party. A person who is subject to service of process must be joined as a party in the action if:
(A)in that person's absence, the court cannot accord complete relief among existing parties; or
(B)that person claims an interest relating to the subject of the action and is so situated that disposing of the action in the person's absence may:
(i)as a practical matter impair or impede the person's ability to protect the interest; or
(ii)leave an existing party subject to a substantial risk of incurring double, multiple, or otherwise inconsistent obligations because of the interest.
(2)Joinder by court order. If a person has not been joined as required, the court must order that the person be made a party. A person who refuses to join as a plaintiff may be made either a defendant or, in a proper case, an involuntary plaintiff.
(b)When joinder is not feasible. If a person who is required to be joined if feasible cannot be joined, the court must determine whether, in equity and good conscience, the action should proceed among the existing parties or should be dismissed. The factors for the court to consider include:
(1)the extent to which a judgment rendered in the person's absence might prejudice that person or the existing parties;
(2)the extent to which any prejudice could be lessened or avoided by:
(A)protective provisions in the judgment;
(B)shaping the relief; or
(C)other measures;
(3)whether a judgment rendered in the person's absence would be adequate; and
(4)whether the plaintiff would have an adequate remedy if the action were dismissed for nonjoinder.
(c)Pleading reasons for nonjoinder. When asserting a claim for relief, a party must state:
(1)the name, if known, of any person who is required to be joined if feasible but is not joined; and
(2)the reasons for not joining that person.
(d)Exception for class actions. This rule is subject to Rule 77.
Amendment History
(Adopted March 1, 2016, effective July 1, 2016.)
Plain-English Summary
Some lawsuits can't be decided without everyone whose interests are on the line. Rule 19 identifies who counts as a required party: someone whose absence would leave the court unable to give complete relief among the people already in the case, or someone who claims an interest in the dispute that absence would put at practical risk, either by impairing that person's ability to protect the interest or by exposing an existing party to double, multiple, or conflicting obligations. If such a person can be served with process, the court must order that they be joined, and a person who won't join voluntarily as a plaintiff can be added as a defendant or, in appropriate cases, as an involuntary plaintiff instead.
Sometimes joining that person isn't possible, perhaps the court has no way to reach them. When that happens, Rule 19 doesn't force dismissal automatically. Instead, the court weighs, in equity and good conscience, whether to proceed without the absent person or to dismiss the case. It looks at how much a judgment might prejudice the absent person or the existing parties, whether that prejudice could be softened through protective terms or by shaping the relief differently, whether a judgment without the missing party would still be meaningful, and whether the plaintiff would have anywhere else to go if the case were dismissed.
When a plaintiff knows of someone who should be joined but isn't, the pleading has to say so, naming the person if known and explaining why they aren't part of the case. This lets the court and the other parties evaluate early whether the case can proceed as filed. The rule doesn't reach class actions, which follow their own joinder framework under Rule 77.
Frequently Asked Questions
What makes someone a "required party" under Rule 19?
Someone without whom the court can't give complete relief, or someone whose absence would put that person's own interest at practical risk or expose an existing party to inconsistent obligations.
What happens if a required party won't join the lawsuit voluntarily?
The court can order them joined as a defendant or, in a proper case, as an involuntary plaintiff.
What if a required party can't be joined?
The court decides, in equity and good conscience, whether to proceed without that person or dismiss the case, weighing possible prejudice, whether relief can be shaped to reduce it, whether a judgment would still be adequate, and whether the plaintiff has another remedy available.
Do I have to disclose in my complaint that someone should be joined but isn't?
Yes. The pleading must name that person, if known, and explain the reasons for not joining them.
Does Rule 19 apply to class actions?
No. Class actions follow the joinder framework in Rule 77 instead.
Source & verification. Rule text
are reproduced verbatim from the Idaho Rules of Civil Procedure, adopted by the
Supreme Court of Idaho. Last verified July 14, 2026. ·
Official source
Also known as:necessary party lawsuitindispensable party rulerequired joinder of partiesjoining a missing partyinvoluntary plaintiff idaho