This Practice Note provides an overview of the different types of expropriation (nationalisation) that may occur under international investment law. If covers the definition of expropriation, the provision in the UK Model bilateral investment treaty (BIT) on expropriation, different types (or forms) of expropriation (direct, indirect and creeping), the issue of what constitutes a regulatory measure and the compensation for investors where a state expropriates an asset (often, required to be prompt, adequate and effective). Claims by investors regarding expropriation (lawful and unlawful) are some of the most common against states in investment treaty arbitration proceedings.