The performance audit is an effective tool in the process of evaluating the management of public money by analyzing whether the entity / program operates efficiently and effectively with respect to economy. The successful achievement of the objectives set within them largely depends on the processes and decisions taken at the audit planning stage. The preliminary study in performance audit planning, as a decisive step, serves as a credible basis for applying auditors' professional judgment and decision-making. The purpose of this study is an examination of the theoretical and applied aspects of performance audit, including the need to conduct a preliminary study in the planning phase in order to determine whether or not to audit a program / entity or activity funded from public financial sources.