The book examines the wide variety of situations in which a duty to make restitution arises by the operation of law, whether by reason of statute or the common law principle of unjust enrichment. It further examines the restitutionary provisions of the Contracts Act 1950, their theoretical underpinnings and historical development, and key distinctions between Malaysian and English law. It also explores complex issues and subject areas such as restitution for wrongs, limitation periods and available defences. Since its publication, the First Edition of this work has been regularly cited in and applied by the superior courts in Malaysia and in landmark decisions of the Federal Court and the Court of Appeal. This new edition has been thoroughly updated to reflect recent case law and developments in Malaysia and other common law jurisdictions, and remains the authoritative reference on restitution and unjust enrichment in Malaysia.