Sempra Metals Ltd v Inland Revenue Commissioners [2007] UKHL 34 is a UK tax law case, concerning the availability of compound interest upon personal claims.
The effect of the case, decided by a majority, was to reverse the outcome of Westdeutsche Landesbank Girozentrale v Islington LBC.
However, the Supreme Court departed from this ruling in Prudential Assurance Co Ltd v Revenue and Customs Commissioners.
Sempra Metals claimed the tax back, as it was paid under a mistake of law, and it demanded compound interest, the time value of the money.
The House of Lords held that there was an action for money paid under mistakes of law, Kleinwort v Lincoln CC.