Adverse opinion
Also known as: Negative opinion, Unfavorable opinion
An adverse opinion is a formal conclusion issued by an auditor stating that the subject matter being audited does not conform to the required criteria. It indicates that misstatements or failures are both material and pervasive, meaning they affect many parts of the system or report. This represents the most severe negative outcome of an audit assessment.
In practice
An auditor issues this opinion when systemic security gaps—such as a total lack of encryption across all databases—render an organization's compliance claims false. It is delivered as the final verdict in an Audit Report or Attestation engagement.