This website uses cookies to ensure you get the best experience on our website. Learn more

Got it!

res judicata

Res judicata is a Latin phrase that translates to “a matter judged.” It is the principle that a cause of action  may not be re-litigated  once there has been a final judgment on the merits . In this context, finality refers to a court’s rendering of such a judgment.

Res judicata is also called claim preclusion, and the terms are used interchangeably. Res judicata is distinct from issue preclusion .

Bar and Merger

Claim preclusion has two main applications:

1. Bar: A losing plaintiff  cannot sue  the same defendant  again on the same cause of action. Example: Plaintiff P sues Defendant D on Cause of Action C and loses. P may not bring another suit against D on C.
2. Merger: A winning plaintiff cannot sue the same defendant again on the same cause of action to obtain additional recovery . Example: P wins against D on C but may not file a new action  against D on C to seek more damages .

A claim can have finality even if no damages are awarded. A prevailing party  who believes damages were inadequate, or who received none, cannot bring another suit on the same cause of action.

Policies Behind Claim Preclusion

Courts uphold claim preclusion to:

• promote judicial efficiency
• ensure fairness
• avoid inconsistent judgments

Judgments Not “On the Merits”

Historically, claim preclusion applied only to decisions on the merits, meaning those based on law  and fact  after evidence is heard. The modern view in most jurisdictions  includes certain dismissals , such as those for failure to state a claim  under Federal Rule of Civil Procedure 12(b)(6).

Under Federal Rule of Civil Procedure 41(b) , the following are not adjudications  on the merits and are not claim-preclusive unless the order  states otherwise:

• lack of jurisdiction

• improper venue

• failure to join a required party under Rule 19

• voluntary dismissals

• dismissals expressly “without prejudice ”

Many jurisdictions also treat dismissal for failure to prosecute  as claim-preclusive, subject to appellate review  for abuse of discretion .

Counterclaims

Rule 13 of the Federal Rules of Civil Procedure  governs counterclaims . Generally, claim preclusion applies to unasserted compulsory counterclaims  but not to unasserted permissive counterclaims . Two exceptions exist:

1. The defendant was unaware that the claim was compulsory (See Dindo v. Whitney, 451 F.2d 1 (1st Cir. 1971 ).
2. The defendant prevails on an affirmative defense  and later counterclaims on the same facts .

Some jurisdictions follow the Common Law Compulsory Counterclaim Rule , barring a later claim  if granting relief  would nullify  a prior judgment.

Other Doctrines with Similar Effect

Estoppel : A party cannot litigate a position inconsistent with earlier conduct on which another party detrimentally relied.

Judicial estoppel: A party cannot take factual positions in current litigation that contradict positions taken in earlier judicial proceedings .

Adverse Parties

Claim preclusion applies only to adverse parties , not to co-parties. By contrast, collateral estoppel  (issue preclusion ) can apply to both.

[Last reviewed in February of 2026 by the Wex Definitions Team
]

Wex

• THE LEGAL PROCESS

• courts

• wex articles

• wex definitions

• civil procedure

• courts and procedure

• legal education and practice