In civil procedure, the term “multiplicity of actions,” or “multiplicity of suits”, refers to the bringing of multiple lawsuits that raise the same issue(s) and that could have been brought in one action. The law generally seeks to avoid multiplicity of actions because inconsistent outcomes could result. Additionally, allowing for unnecessary multiple suits is “a harm to society's legitimate interest in judicial efficiency. Courts are a public resource, providing publicly financed resolution of private disputes.”
Consideration of the possibility of multiplicity of actions is present in numerous areas of civil procedure. For example, Rule 13(a) of the Federal Rules of Civil Procedure (FRCP) establishes the federal practice of compulsory counterclaims. Although the rule does not directly reference multiplicity of actions, the possibility is “precisely the evil the federal approach to counterclaims was fashioned to avoid.” Likewise, the purpose of FRCP 14 in establishing the third-party impleader is “to avoid circuity of actions by disposing of an entire subject matter arising from one set of facts in one action.” Additionally, courts may apply mandatory joinder of parties to avoid “the undesirability of duplicative litigation.”
[Last updated in June of 2020 by the Wex Definitions Team]