This chapter, along with Chapters 5 to 6, examines the legal duties that constrain accumulation once a charity has been created. Controller duties (e.g. directors’ duties and trustee duties) are the focus of this chapter. Clearly, duties of loyalty, good faith and of care and diligence can potentially play a restraining role in relation to agency costs, the risk of which can be heightened by accumulation. Further, controller duties also raise the possibility of regulating the retention and distribution of charity assets by controllers, thus affecting the intergenerational distribution of benefits. The chapter provides an overview of the controller duties arising from each of the main legal forms adopted by charities and analyzes the impact of those duties on accumulation. Particular attention is paid to duties arising on the exercise of discretionary powers, such as the duties to act upon genuine consideration and to act impartially. Examples are provided primarily from Australia, the United Kingdom and the United States.