The Supreme Court has today handed down its unanimous judgment in SKAT v MCML Ltd [2026] UKSC 19, clarifying the true scope of the doctrine of issue estoppel.
The judgment by Lord Sales and Lord Doherty (with whom Lord Lloyd-Jones, Lady Rose and Lady Simler agreed) allowed the appeal, holding that the Court of Appeal should not have dismissed a substantial fraud claim brought by SKAT, the Danish tax authority, against MCML Ltd (previously known as ED&F Man Capital Markets Ltd).
The Supreme Court’s judgment, which is likely to shape the evolution of issue estoppel in England and Wales, and in the rest of the common law world, offers guidance on a number of significant issues concerning the scope of issue estoppel.
First, the Court held that an issue estoppel arising from one set of facts should not be expanded to cover another set of facts, even if the factual differences would have been immaterial to the prior decision. Rather, the relevant issue is to be identified “by reference to the pleaded claim for the relief sought (or defence raised)” and issue estoppel “arises only in respect of the particular claim brought (or defence raised) in the proceedings”: [44]. This is the first time in 87 years (since New Brunswick Railway Co v British and French Trust Corporation [1939] AC 1) that this question has been considered at the highest appellate level.
Second, the Supreme Court clarified the meaning of the requirement that a determination must have been ‘necessary’ and ‘fundamental’ to the prior decision for it to give rise to issue estoppel. The Court held that, when applying this test, it was necessary to focus on “the facts that are fundamental or ultimate (in the sense that they necessarily had to be established to make good the cause of action being alleged or a defence put forward) and the legal quality of those particular facts”: [46]. Thus, the “immediate foundation of the ultimate decision” may give rise to an issue estoppel whereas “elements of the prior court’s reasoning leading up to that decision cannot”: [45].
Third, the judgment offers an authoritative explanation of the distinction between issue estoppel and the doctrine of precedent. The legal effect of an issue estoppel is more far-reaching than the legal effect produced by judicial precedent in the sense that the issue estoppel, once established, cannot be distinguished or overruled: [39]. Accordingly, identifying the ‘issue’ for the purposes of issue estoppel requires a different, and narrower, interpretive process than identifying the ratio decidendi of a case: [51].
Fourth, the Supreme Court held that, when settling the limits of issue estoppel, it was necessary to have regard to the law on abuse of process, which is a distinct aspect of the law of res judicata that guards against unfairness arising from successive litigation of the same or similar points. “It would be contrary to the coherent application of the law in this area, and would work injustice, to give the doctrine of issue estoppel an expansive interpretation which cut across and significantly displaced the rules on abuse of process”: [50].
In this respect, and more generally, the judgment is a salutary reminder of the need to keep issue estoppel “within the narrow limits which are appropriate for a doctrine” which has the “powerful effect” of denying a litigant their right to access the court: [1], [38], [51]–[52].
Charles Graham KC and KV Krishnaprasad (led by Lord Pannick KC) acted for SKAT, the successful appellant, instructed by Pinsent Masons LLP.
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