The purpose of this study is to determine the requirements for the observance of the principle of independence by external and internal auditors, given their relationship in the performance of audit engagements. Research methodology. The methodological and theoretical basis of the study is the scientific and creative understanding of the developments of foreign and national scientists in the field of auditing in general, and internal audit in particular. The information base of the study was the official documents, standards and codes of ethics of international professional associations and organizations of accountants and auditors. To achieve this goal, a set of general scientific methods (analysis, synthesis, induction, deduction, abstraction) and methodological techniques (systematization, generalization, review, comparison) to study the principle of independence in the practice of external and internal audit as a professional activity have been used. Results. The necessity of developing a detailed Code of Ethics for Internal Auditors and specific regulations for internal audit services, which would combine the requirements of official standards and codes, and identify clear measures to assess conflicts of interest and precautionary measures, has been substantiated. The main stages of development of appropriate precautionary measures at such levels as level of auditor, level of engagement, functional level, and organizational level have been determined. It has been proved that the independence of thought and behavior as components of the independence of both external and internal auditors should be formed in view of all parties involved in the process of performing the audit engagement, taking into account the content of three party relationships. The practical significance of the research results. The practical use of the proposed theoretical approaches and practical recommendations will improve the quality of engagements performed by both external and internal auditors.