SIGMA Brief 28 aims to give guidance to auditors dealing with public procurement processes. Based on audit experience, it examines the stages that are worth looking at and explains why. It highlights those aspects that are recommended to be considered in more detail. It also gives advice as to which documents the auditor is suggested to scrutinise in order to find evidence. Brief case studies, where available, and checklist questions for the auditor illustrate the main aspects. The Brief mainly concentrates on individual procurement procedures but concessions and public-private partnerships are also touched on at the end of the Brief.