Joinder of issue describes the point in civil or criminal proceedings when the parties’ positions are clearly opposed on the facts and/or law, so that there is a defined dispute for the court to determine. It commonly arises when a defendant serves a defence (or, in criminal cases, enters a plea), putting the claimant’s or prosecutor’s case “in issue”.In England and Wales and Northern Ireland, the concept is reflected in the Civil Procedure Rules and criminal procedure, but “joinder of issue” is largely used as a descriptive procedural term rather than a statutory definition. In Ireland, the expression is likewise used in pleadings and procedural texts to mark when matters are formally contested. In Scotland, similar ideas exist through the closing of the record or fixing the proof, though the specific phrase “joinder of issue” is less frequently used.Practically, joinder of issue is important for case management, disclosure, evidential preparation and the framing of issues for trial or proof. It defines what is admitted, what is denied, and what the court must adjudicate, and can affect costs, burden of proof and the scope of argument at hearing.