Editorial note. This Case Note is a short, plain-English summary and our editorial opinion. It may not capture every issue in the case, may contain errors or become out of date, is not legal advice, and must not be relied upon. Always read the full judgment (linked below) and take advice from a qualified lawyer before acting.

When does losing one claim stop you bringing another? On 1 July 2026 the Supreme Court gave its most substantial guidance on issue estoppel in years — and revived the Danish tax authority's claim against a London brokerage in the process. In Skatteforvaltningen v MCML Ltd [2026] UKSC 19, the Court unanimously allowed SKAT's appeal, holding that the dismissal of its 2018 claim did not bar a fresh claim issued in 2022.

What the case was about

SKAT, the Danish customs and tax administration, has spent years litigating in London to recover sums paid out on applications for refunds of Danish dividend withholding tax. MCML — formerly ED&F Man Capital Markets — was one of the defendants. SKAT's 2018 claim against it was dismissed; in 2022 SKAT issued a further claim concerning different tax vouchers. The Court of Appeal (by a majority) held the new claim was barred by issue estoppel: the doctrine that prevents a party re-contesting an issue already decided against it in earlier proceedings between the same parties — as the Supreme Court noted at para 1, a doctrine so powerful that it holds even if the earlier outcome was wrong in law.

What the Supreme Court decided

In a joint judgment of Lord Sales and Lord Doherty (with whom Lord Lloyd-Jones, Lady Rose and Lady Simler agreed), the Court held that no issue estoppel arose and the 2022 claim should not have been dismissed (para 61). An issue estoppel attaches to a determination of the legal quality of a specific set of facts that was fundamental to the earlier decision — not to broader propositions abstracted from it. The Court explained the House of Lords' decision in Watt v Ahsan as an orthodox application of those principles rather than an extension of them (para 59), and respectfully rejected both the majority's formulation and Nugee LJ's narrower formulation below (para 60). Because the 2022 claim concerned different vouchers — a different subject matter — the earlier dismissal did not preclude it.

Why it matters

  • A recalibration every commercial litigator should note. Issue estoppel is pleaded constantly; the Supreme Court has now tightened the focus on precisely what the first court necessarily decided, and about what facts. Broad, issue-shaped formulations will no longer do.
  • Losing a claim is not losing a theme. Where later proceedings concern different subject matter — here, different refund applications — a claimant is not estopped merely because the legal question feels familiar.
  • The SKAT litigation continues. One of the largest foreign-revenue recovery efforts ever run through the English courts has fresh life against this defendant.

Explore the underlying law on Search the Law: issue estoppel and res judicata · second claims and Henderson abuse.

Read the full judgment: Skatteforvaltningen v MCML Ltd [2026] UKSC 19 (The National Archives).