A class action is a lawsuit in which multiple plaintiffs come together to sue a defendant as a group. A class action notice is an invitation to join such a lawsuit.  If, together with other people, you have been injured by a common defendant, then one of the victims can file a personal injury claim and send you an invitation (notice) to join in the lawsuit. Here are the two ways you can respond to a class action notice:

Opt In

In most cases, you don't have to do anything once you receive a notice; you automatically become part of the class (group of plaintiffs). In a few cases, you need to take an active step to join the class. The step to take will be explained in the notice. For example, you may be required to fill an online form or send a mail declining the invitation.

This is why it's important to read "junk" mail originating from personal injury attorneys. You may ignore a class action notice thinking that you are done with it, but that may mean you are a member of a class action if the notice automatically makes you a member of the class. At the other end of the scale, ignoring mail that requires an official opt-in step means that you are out of the suit and have no share in the potential settlement.

Opt Out

In most cases, there is no downside to joining a class action. However, you may wish to stay out of it so that you can pursue your own legal action against the defendant. You may wish to do this, for example, if you believe that your injuries are far greater than those of the other defendants, and you wish to pursue a settlement commensurate with those injuries.

The procedure for opting out of the class action will be contained in the notice. In most cases, you will be required to notify the attorneys representing the class of your decision to opt out of the lawsuit. Note that there may be a deadline after which you cannot opt out, so this is another incentive for fully reading all class action notices.

It's a good idea to consult an attorney before opting out of a class action, even if you wish to file a separate lawsuit. Consider an example where the defendant doesn't have deep pockets, and the class members collect all his or her assets as their settlement. In such a case, you may not be able to collect your judgment even if you win your lawsuit.