ISO 19011 sets out 4 headings in determining auditor competence. They apply equally to internal auditors and to lead auditors. namely,
General: Organizational knowledge, skills and experience; working experience is essential.
Personal behaviour: A range of personal attributes and professional behaviours are needed including ethical, open-minded, diplomatic, observant, perceptive, tenacious, decisive, culturally sensitive, ability to act with fortitude, etc.
Knowledge and skills: To successfully complete an audit, generic competence (including auditing skills) and a level of discipline and sector-specific knowledge and skills (i.e. of the applicable ISO Standard and of the economic sector being audited) are required.
Achieving Auditor Competence: After ISO Auditor Certification building experience by regular participation audits.