The plaintiff, the (person/entity) suing must be the person/entity that has the claim. It must be the party that was injured by the defendant. Only "persons" can be a plaintiff. Under the law, a person is either a natural person (human being) or a recognized business "entity" (e.g. corporation, L.L.C. etc). A "d.b.a" (doing business as) or trade name is not an entity.
For example, my law firm is Berkus Law Office, P.C. (a professional corporation). However, I operate under various trade names, such as "Advanced Bankruptcy". So, if my business needed to sue someone (e.g. a client for not paying their bill) the plaintiff would be "Bekrus Law Office, P.C. d.b.a. Advanced Bankruptcy".
There are any number of things necessary for a judgment to be valid. However, from the context of your question, it appears that you are concerned with who may be a plaintiff in a lawsuit for the judgment to be enforceable. First of all, the plaintiff MUST be the legal entity (natural or artificial - ie, a human being or an LLC, Corporation, Probate Estate, Bankruptcy Estate, etc) that currently owns the debt or is entitled to some remedy for a breach or violation of their (it's) rights. If you owed money to an artificial entity, and if that entity does business under a legitimate "dba", then they can sue you under the entities legal name, and "doing business as" ... whatever. This holds true for any business, entity, or person that purchases or somehow acquires the right to collect from you from another person or entity that you owe. It is important that you meet with a local attorney for a review of the specific matter that you are concerned about. Good Luck!
There must be a plaintiff who suffered a cognizable injury or damages as a result of some action on the part of someone called a defendant.
That plaintiff must either be a real person who's alive, or a recognized artificial entity such as a corporation, a partnership or some other organization like an unincorporated association which has a corporate existence. All artificial entities exist by virtue of some statute that authorizes the state to charter, organize or incorporate such entities.
A person or corporate entity may also conduct business as a D/B/A. But the actual party in interest who goes by a D/B./A must identify their actual name and D/B/A.
There must be a cognizable cause of action either created by statute or existing as a matter of common law, or subsequent decisional law.
There must also be some evidence behind the cause of action that the defendant is indebted to the Plaintiff for the injury or damages. In a trial, the evidence is presented to the judge or jury and the facts are decided and the judge applies the law to the verdict or makes findings of fact if there is no jury. Usually the evidence is put on through stipulation or by disputed evidence from both sides.
If there is a default entered, the well-pleaded allegations of the complaint are taken as true, and the plaintiff must establish by sufficient evidence, the amount of damages claimed.
Furthermore, the trial court must have jurisdiction over the defendant and the plaintiff.
If there is no personal jurisdiction over either or both, then there can be no valid judgment. In the case of a plaintiff, there may be a requirement by rule or statute, that the plaintiff be a resident of the jurisdiction where the action is brought before that party can bring the action. In the case of the defendant, the defendant must be amenable to jurisdiction over his/her/it based on residency or conducting activities in the jurisdiction.
There also has to be subject matter jurisdiction. That means that the court is authorized to hear disputes of the nature and kind presented, or the entity or person suing has standing to bring the action. If the state brings a civil case, and it turns out there is no statute authorizing the state to bring that kind of action against that type of defendant, then there is no subject matter jurisdiction.
There may be other jurisdictional limits such as the amount in controversy or the kind of relief sought can only be brought in specialized courts per statute.
Assuming all the issues concerning standing and the kind of case is met, the defendant is amenable to suit in the jurisdiction, then with a cause of action well -pleaded and evidence of liability and damages presented, its probably going to be a valid judgment.
The only other challenge is service of process or the failure to join all interested parties. If the complaint was served on a defendant in a way not authorized by law, or it was served on the wrong person, then the judgment is void for lack of proper notice. If the plaintiff failed to join all interested persons in the same case, that can also destroy a judgment.
This is a public forum. Any questions or answers published here should not be construed as the giving or receiving of legal advice or the formation of any attorney-client relationship. You should consult with a competent attorney in the jurisdiction where your legal issues are pending and get good, solid legal advice. This being a public forum, those answers you do read are merely given for informational purposes only.