Substitution of parties refers to the procedural step by which one party to legal proceedings is replaced by another, without the need to start a fresh claim or action. It commonly occurs where a party has died, become insolvent, lost or acquired an interest in the subject matter of the proceedings, or where the wrong entity was originally named (for example, a misdescribed company or public body).In England and Wales and Northern Ireland, the Civil Procedure Rules and equivalent court rules govern substitution of claimants and defendants, including limitation implications and requirements for the court’s permission. In Ireland, similar provision is made in the Rules of the Superior Courts and other court rules. In Scotland, the concept is broadly similar but is dealt with under the rules on alteration of parties in the Ordinary Cause Rules, Court of Session Rules and other procedural codes.Across the UK and Ireland, substitution of parties is a practical mechanism to ensure that litigation continues with the correct parties bound by, and able to enforce, any judgment, while preserving accrued rights and avoiding unnecessary duplication of proceedings.