Res Judicata and Collateral Estoppel: When a Business Is Sued Again Over a Dispute Already Decided

Last updated: November 2026. Reviewed by Pavel Kolmogorov, California business litigation attorney (State Bar No. 321018).

Res judicata, also called claim preclusion, bars a second lawsuit on the same cause of action between the same parties after a final judgment on the merits. Collateral estoppel, or issue preclusion, bars relitigating an issue that was actually litigated and necessarily decided, even in a suit on a different claim. California decides whether two suits involve the same cause of action by looking at the harm suffered, not the legal theory. Kolmogorov Law, P.C. raises and answers these defenses for businesses in the California courts.

Call (909) 235-6116 or contact us online to discuss a second lawsuit over a dispute you thought was finished.

Res judicata and collateral estoppel do different jobs

The California Supreme Court restated both doctrines in 2015 and settled on the modern names. Claim preclusion arises when a second suit involves the same cause of action, between the same parties or those in privity with them, after a final judgment on the merits in the first suit. When it applies, it bars the claim altogether, including matters that should have been advanced the first time.

Issue preclusion is narrower in one way and wider in another. It applies after a final adjudication of an identical issue that was actually litigated and necessarily decided in the first suit. It can be asserted only against someone who was a party to that suit or in privity with one. It reaches a later case even if that case raises a different cause of action. (DKN Holdings LLC v. Faerber (2015) 61 Cal.4th 813.)

A judgment is conclusive, as to the matter directly adjudged, between the parties and, on stated conditions, their successors in interest. (Code Civ. Proc., § 1908, subd. (a)(2).) Only that is deemed adjudged which appears on the face of the judgment or was actually and necessarily included in it. (Code Civ. Proc., § 1911.)

What counts as the same cause of action

California uses the primary rights theory. For this purpose a cause of action is the right to obtain redress for a harm suffered, regardless of the remedy sought or the legal theory advanced. One injury gives rise to one claim for relief. When two actions between the same parties seek compensation for the same harm, they generally involve the same primary right. (Boeken v. Philip Morris USA, Inc. (2010) 48 Cal.4th 788, 798.)

A supplier sues a customer for breach of a supply agreement, loses at trial, and files again two years later. The new complaint pleads fraud and unfair competition, but it seeks the same lost profits from the same terminated agreement. The labels are new and the harm is not, so the customer has a claim preclusion defense. A later, separate breach that causes new harm raises a harder question and needs its own analysis.

Who is bound and who may use the earlier result

Claim preclusion requires the same parties or their privies on both sides. The Supreme Court held in DKN Holdings that co-obligors who are jointly and severally liable are not in privity with each other for that reason alone. A judgment against one of them does not, by itself, bar a later suit against another.

For issue preclusion, a person who was not a party to the first case may invoke it, as long as the party it is used against was bound by that case. In DKN Holdings the court noted that a later-sued co-obligor could use the earlier judgment to stop the plaintiff from relitigating the amount of the loss.

A person who is not a party but controls an action, and has a proprietary or financial interest in the judgment or in the question decided, is bound as if a party. (Code Civ. Proc., § 1908, subd. (b).)

Dismissals, settlements, awards, and declarations

• Dismissal with prejudice. For purposes of res judicata it is the equivalent of a final judgment on the merits and bars the entire cause of action. (Boeken, supra, 48 Cal.4th at p. 793.)
• Voluntary dismissal without prejudice. It is not a judgment on the merits. Our page on voluntary dismissal covers what the plaintiff may still do.
• Settlement. A dismissal with prejudice that follows carries the preclusive effect, and the release governs the rest. What a release reaches depends on its words, which our page on settlement agreements and releases covers.
• Arbitration award. Once an award is confirmed, the judgment entered on it has the same force and effect as a judgment in a civil action. (Code Civ. Proc., § 1287.4.) An award that has been neither confirmed nor vacated has the force of a written contract between the parties. (Code Civ. Proc., § 1287.6.) See our page on confirming or vacating an arbitration award.
• Declaratory judgment. A judgment under the declaratory relief chapter does not preclude a party from obtaining additional relief based on the same facts. (Code Civ. Proc., § 1062.) The Supreme Court has confined that exception to purely declaratory judgments, so a plaintiff that also won coercive relief, such as specific performance, faces ordinary claim preclusion. Our page on declaratory relief explains that remedy.

The related trap: claims you had to bring the first time

A defendant can lose its own claims without any judgment against it. A party served with a complaint must plead, by cross-complaint, any related cause of action it has against the plaintiff when it serves its answer. If it does not, it may not later assert that claim against the plaintiff in another action. (Code Civ. Proc., § 426.30, subd. (a).) The rule does not apply if the party never answered, in small claims court, or where the first complaint sought only a declaration of rights. (Code Civ. Proc., §§ 426.30, subd. (b), 426.60.) Our page on cross-complaints explains what counts as related.

If your company is sued a second time

Collect the record of the first case before anything else: the complaint, the judgment or dismissal, any statement of decision or verdict form, and the settlement agreement. Then compare harm to harm, not label to label.

An answer must state any new matter constituting a defense, and preclusion is ordinarily pleaded there. (Code Civ. Proc., § 431.30, subd. (b)(2).) Whether it can be decided sooner, on a demurrer, depends on what appears in the new complaint and in the court records.

A plaintiff planning a second suit should run the same comparison in reverse.

What to bring to the first meeting

• The complaint, answer, and any cross-complaint from the first case.
• The judgment, dismissal, statement of decision, verdict, or arbitration award.
• The settlement agreement and release, if there was one.
• The new complaint.
• A short list of who the parties were in each case and how they are related.

Frequently asked questions

We won a lawsuit two years ago and the same company has sued us again over the same contract. Can they do that?

They can file, but claim preclusion may end the case. In California a final judgment on the merits bars a second suit between the same parties on the same cause of action, and the cause of action is defined by the harm suffered. If the new complaint seeks redress for the same injury, the earlier judgment is a bar even though the legal theory is new.

We settled and the case was dismissed with prejudice, but now the other side is suing our parent company on the same facts. Does the dismissal protect it?

Possibly. In California a dismissal with prejudice is treated as a final judgment on the merits, but claim preclusion protects only the same parties and those in privity with them. Whether a parent company is in privity depends on its relationship to the first case. The release in the settlement agreement may protect it more directly, so read its definition of released parties.

What is the difference between res judicata and collateral estoppel?

Res judicata, or claim preclusion, bars an entire cause of action that was or should have been litigated in an earlier California case between the same parties. Collateral estoppel, or issue preclusion, bars only specific issues that were actually litigated and necessarily decided, but it applies even when the second case involves a different claim.

Does a dismissal without prejudice have res judicata effect?

No. Claim preclusion in California requires a final judgment on the merits, and a voluntary dismissal without prejudice is not one. The plaintiff may file the claim again if the statute of limitations allows. A dismissal with prejudice is different and bars the same cause of action against the same party.

Is an arbitration award res judicata in California?

A confirmed award is entered as a judgment, and California Code of Civil Procedure section 1287.4 gives that judgment the same force and effect as a judgment in a civil action. An award that has been neither confirmed nor vacated has the force of a written contract between the parties under section 1287.6.

Talk to a California business litigation attorney

If your company is facing a second lawsuit over a finished dispute, or you need to know what an old judgment or dismissal still allows, call (909) 235-6116 or contact us online. Kolmogorov Law, P.C. is a business litigation firm in Irvine, California. See also our civil litigation page.

This page provides general information about California law and is not legal advice. Outcomes depend on the record of the earlier case, the parties, and the court.