Subject. The article investigates the rationality of internal controls in accordance with COSO-INTOSAI recommendations in public sector organizations. Objectives. The aim is to classify the reasons for failures and the actual refusal to directly follow the COSO-INTOSAI recommendations in public sector organizations in Russia and the UK, as well as to determine the directions for the rational development of internal control in such organizations. Methods. The study employs the content analysis of domestic and foreign sources, the comparative analysis. Results. The study classifies the reasons for failures, i.e. excessive universalism and inanity of recommendations borrowed from professional participants of the financial market, hiring employees from financial markets, erroneous creation of additional units, procedures and documents, objective lack of authority, motivation and qualification of employees to implement the recommendations. The areas of rational development are determined on the basis of sector specifics, real powers of budget fund managers, professional duties of chief accountants as controllers, reasonable centralization and digitalization of public services. Conclusions. The findings may clarify the regulatory and departmental documents of the Ministry of Finance and managers of budget funds in internal control of public sector organizations, and improve the performance of such organizations, increase the efficiency of budget spending and off-budget operations.