Outcome Responsibility and Autonomy: Rationalising the Change of Position Defence in Mistaken Payment Claims

Three decades on from its decisive advent in England and Australia, the change of position defence has become part of the fabric of the law of restitution. Yet its rationale — long neglected but increasingly scrutinised — remains a matter of debate. This article seeks to advance the debate by analysing possible rationales for the defence as it applies to the paradigm case of restitution, mistaken payments. After exposing difficulties with many of the candidates that have hitherto attracted support, this article advances two rationales better suited to facilitate principled development of the defence: outcome responsibility, and reciprocal recognition of decisional autonomy. Both rationales put the defence on firm normative foundations, align with its present contours and suggest areas for further development.