(1) A person who obtains something as a result of the performance of another person or otherwise at that person’s expense without legal grounds for doing so is under a duty to surrender to that person what has been obtained. This duty also exists if the legal grounds later cease to exist or if the result intended to be achieved by an act of performance in accordance with the substance of the legal transaction does not materialise.
(2) Performance also includes the acknowledgement of the existence or non-existence of an obligation.