An audit is a comparison of observed activities and/or results with documented requirements. The evidence provided from audits forms the basis of improvement in either the element audited, or in the requirements. Effective quality auditing can prevent problems by uncovering situations that, while still acceptable, are trending toward an eventual problem. The attention of management brought on by an unfavorable audit report can often prevent future noncompliance.
ISO 19011, Guidelines for Auditing Quality Systems, defines a quality audit as a
systematic, independent and documented process for obtaining audit evidence ...