Sempra Metals Ltd v Inland Revenue Commissioners
[2007] UKHL 34
Ratio Decidendi
Compound interest may be awarded as a restitutionary remedy where the defendant has been unjustly enriched by the use of money over time. The previous restriction to simple interest only was overruled.
Facts
Sempra Metals (formerly Metallgesellschaft) overpaid advance corporation tax under a regime later held to be contrary to EU law. It claimed restitution including compound interest.
Judgment Summary
The House of Lords held (by majority) that compound interest could be awarded as restitution for the time value of money wrongfully retained. This overruled the previous position that only simple interest was available.
Key Quotes
"In principle, where a claimant seeks a restitutionary remedy for the time value of money paid to the defendant, compound interest may be awarded."
— Lord Nicholls
Subsequent Treatment
Established the availability of compound interest as a restitutionary remedy, though some aspects were doubted in Prudential Assurance v HMRC.