In the given article I have analyzed the content of the requirements of regulatory documents for internal audit of accredited organizations’ management systems. I have shown that the existing differences in requirements for internal audit of management systems depend on the type of accreditation or certification. For example, GOST R ISO / IEC 17021-1, GOST ISO / IEC 17025, GOST R ISO 9001. This is a complex organizational task, caused by the unstructured presentation of the corresponding text, differences in the terminology used, and different requirements. To solve it, I have recommended developing and applying in the organization a single documented internal audit procedure (IA) that meets the recommendations of GOST R ISO 19011. I have noted that special attention should be paid to the competence of the audit participants, primarily auditors and technical experts. Combined IA may be recommended for units of certified organizations performing work in accredited areas of activity. Identifying new not yet unidentified risks and other opportunities for improvement may be one of the effective approaches to improving the organization’s IA processes. In conclusion, I have given recommendations on the implementation of the internal audit of accredited organizations' management systems.