The appeal in NASIR v ZAVARCO plc (2025) UKSC 5 concerned the scope of the longstanding English law doctrine of merger. In short, the question is whether the doctrine, by which a cause of action merges with a judgment in the action, applies to a declaratory judgment. The Supreme Court held that it does not.
The doctrine of merger was developed as a means to promote finality in litigation and to prevent duplicative and vexatious litigation. Unlike the standard defence of res judicata in the form of cause of action estoppel, which prevents the contradiction of an earlier judgment as to the existence or non-existence of a cause of action, merger was designed to make a litigant seek his or her remedies in one action by extinguishing a cause of action when judgment has been given on it. Read more »