There is increasing concern with the cost effectiveness of charities' fund-raising activities. Using a recent decision of the US Supreme Court as a backdrop, this paper examines the regulation of professional fund-raising and the associated issues relating to fund-raising costs. Whilst there are no legal limits on fund-raising costs in England and Wales, there are some elements of legal regulation which may indirectly impose some limitations on costs. As well as these legal tools, a number of other mechanisms, both current and proposed, which may help donors to decide which charities to support, taking into account their fund-raising efficiency, will also be considered. The paper finally acknowledges that whilst limiting the costs of fund-raising is a desirable objective, achieving this aim is by no means simple. It is hoped that current and proposed measures based on the theory of ‘let the donor’ decide will help to achieve this aim.