The Ultimate Guide to Federal Rule 23

Class action lawsuits allow a single lawsuit to represent a large number of plaintiffs as a single entity known as a “class.” Before a lawsuit can continue as a class action, a judge must decide if the plaintiffs are all similar enough to proceed as a class. In federal court, this process, which is called “class certification”, is governed by Rule 23 of the Federal Rules of Civil Procedure.

What Is Rule 23 of the Federal Rules of Civil Procedures?

Rule 23 of the Federal Rules of Civil Procedure is the portion of the law that establishes the rules for the federal class certification process. Through the certification process, the judge must determine whether the plaintiffs meet the legal requirements for a class. A class must be certified before the case can proceed as a class action.

What Qualifies for a Class Action Lawsuit?

Federal Rule 23(a) creates four qualifications for a class action lawsuit to be certified: numerosity, commonality, typically, and adequacy.


For the numerosity prerequisite to be satisfied, there must be a large enough number of plaintiffs to justify proceeding as a class action lawsuit. Rule 23 describes this requirement as whether “the class is so numerous that joinder of all members is impracticable.”


With the commonality requirement, the class member’s claims must be sufficiently similar to handling them in a single case. Under Rule 23, commonality is defined as whether “there are questions of law or fact common to the class.”


When a class action is originally filed, it will only be filed in the name of certain plaintiffs who serve as “class representatives.” During the certification process, the court must determine whether the class representatives can represent all the other putative class members. In deciding typicality, Rule 23 requires a judge to determine whether “the claims or defenses of the representative parties are typical of the claims or defenses of the class.”


Under Rule 23, the adequacy requirement demands that “the representative parties will fairly and adequately protect the interests of the class.”

Rule 23(b) Requirements

On top of the four conditions included in Rule 23(a), Rule 23(b) requires that a class also meet one of the following qualifications to be certified:

Prosecuting separate actions would create a risk of inconsistent or varying adjudications with respect to individual class members
Prosecuting separate actions would create a risk of adjudications with respect to individual class members that, as a practical matter, would be dispositive of the interests of the other members not parties to the individual adjudications or would substantially impair or impede their ability to protect their interests.

The party opposing the class has acted or refused to act on grounds that apply generally to the class so that relief is appropriate respecting the class as a whole.

Questions of law or fact common to class members predominate over any questions affecting only individual members, and that a class action is superior to other available methods for fairly and efficiently adjudicating the controversy.

How Many Plaintiffs Do You Need for a Class Action Lawsuit?

While you do not need a specific number of plaintiffs for a class action lawsuit, Rule 23 requires that “the class is so numerous that joinder of all members is impracticable.” For this qualification to be satisfied, there must be so many plaintiffs that it would be challenging to bring them all to court to litigate their claims individually.

Courts will generally refuse to certify classes that do not involve at least a couple dozen putative members. Judges generally will conclude that the numerosity requirement is satisfied if there are over 40 class members, but will rarely certify a class with fewer than 20 plaintiffs.

Is Class Certification Appealable?

Yes, class certification is appealable. However, it is completely up to the court of appeals whether it will accept the appeal, and the court is not required to do so.

Federal Rule of Civil Procedure 23(f) states that a federal appellate court can choose to allow an appeal from an order granting or denying class action certification if a petition is filed within 14 days. The rule does not create any standards for how the court should decide whether to accept an appeal and does not place any limits on the court’s discretion.

What Happens When a Class Certification Is Denied?

If class certification is denied, the case will proceed as an individual lawsuit on behalf of the class representatives only. The putative class members can file their own lawsuits to pursue compensation for their individual injuries.

When Should I Contact a Class Action Lawyer?

If you’re a class member for an existing class action lawsuit, you should receive a notification, often by mail, that explains how to join. In many cases, you will be automatically included in the class and won’t need to contact a class action lawyer. However, some cases do require you to contact the attorney in charge, so make sure you review the notice carefully.

If you think you should be part of a class but don’t receive a notification, you can usually find the information you need to join the class through online research. Many class action lawsuits have created websites that provide information about the case. You will often need to contact a class action lawyer to join the class in these situations, but the website should detail the specific process for joining.

If you have suffered injuries in a situation that you think could warrant a class action lawsuit and there is no existing case, you should contact a class action lawyer as soon as possible to learn more about your options.

Have Questions?


The Class Action Guide to Certification Hearings

How to Join a Class Action Lawsuit