The charity sector has major economic, cultural and social impacts on society. To maintain confidence and build trust, good accounting and reporting systems are essential. Indeed, such could be viewed as necessary conditions for the health and growth of the sector. Well-developed and appropriate accounting and reporting systems (particularly with respect to performance) can help charities discharge accountability to external stakeholders and establish legitimacy in wider society. This paper explores and compares performance reporting by large charities in the United Kingdom (UK) (which has a more-established regulatory architecture) and in the Republic of Ireland (RoI) (which has a much-less developed regulatory framework) at a time when new reporting regulations are being introduced. Through an analysis of the annual reports and annual reviews of 50 large charities, this paper highlights continuing weak performance accountability in both jurisdictions (especially in the RoI). The implications of this are discussed. It is argued that much has yet to be done by charities themselves, and by those concerned with the administration and control of the sector, to rectify this weakness and provide a foundation for better accountability, legitimacy and trust.