A useful internal audit follows the process and the evidence.
An internal audit should tell management whether planned quality arrangements are being followed and whether the processes achieve their intended results. That requires more than asking whether a procedure exists. An auditor may follow a customer order through contract review, purchasing, service delivery and complaint handling, comparing records with interviews and actual work.
The ISO 9001 Internal Auditor Course explains how to establish audit objectives and criteria, select relevant activities and ask questions that reveal control effectiveness. If a warehouse maintains an impressive checklist but regularly ships incorrect quantities, the auditor should investigate the process rather than rely on the existence of the form.
Internal auditors need independence from the work they assess where practicable, professional judgement and a clear understanding of the organisation’s defined QMS scope.