Given the growing demand for accountability in the public sector, there is a need to begin to investigate audit pricing issues in markets within this sector. This study makes three principal contributions. First, it develops and estimates, for the first time, a model of audit fee determinants relevant to the charity sector. The model is based on 210 of the top 500 UK charities with average incoming resources of £27 million. As in previous private sector company studies, size, organisational complexity and audit firm location are the major determinants. A positive association between audit fees and fees for non-audit services is also observed. Charity sector factors of empirical significance include the fundamental nature of the charity (i.e., predominantly grant-making or fund-raising), the importance of trading as a source of charity income and the charity's activity. Separate models are developed for grant-making and fund-raising charities, the results reflecting the relative complexity of the audit of fund-raising charities.Second, the lower auditor concentration in the charity sector market, compared to the private sector market, permits a more powerful test of whether large firms and/or auditor expertise are rewarded with a fee premium. The results show that Big 6 audit firms receive higher audit fees (18.5%, on average) than non-Big 6 firms for audits of fund-raising charities. There is also evidence that non-Big 6 audit firms with expertise in the sector are rewarded with a fee premium over other non-Big 6 firms, again in the more complex audit environment of fund-raising charities.Finally, the study demonstrates that the charity audit fee rate is significantly lower than that of private sector companies; in fact it is approximately half. Further research that discriminates between alternative explanations of this differential is called for. A change in the reporting of charity audit fees is proposed to reflect any element of 'charitable giving' by the audit firm.