This manual was developed to serve as guidance on non-conformance and corrective actions which have been identified as the major problems in the implementation of an effective quality assurance programme. The scope of this manual, while fully addressing the requirements in the governing NUSS programme documents, also covers corrective action processes which would more generally assist users in developing good practices for improved performance in all areas of safety, reliability and economics, and it offers a practical model and illustrative examples of the means by which effective measures and actions can be implemented. Contents: 1. Introduction; 2. Description of corrective action process; 3. Identification of deficiencies; 4. Assessing and correcting deficiencies; 5. Root cause analysis; 6. Verification and follow-up; 7. Implementing procedures; 8. Trend analysis; 9. Summary; Definitions; References; Annex A: Example of a hold for QA clearance tag; Annex B: Examples of non-conformance report forms; Annex C: Example of a reject tag; Annex D: Example of a checklist for reviewing non-conformance dispositions; Annex E: Examples of a stop work notice and stop work notice tag; Annex F: Examples of a deficiency report form and deficiency report–work order forms; Annex G: Example of a list defining a significant event for a nuclear power plant; Annex H: Example of a method for evaluating personnel caused deficiencies; Annex I: Example of a procedure for escalation to higher levels of management to achieve corrective action; Annex J: Example of a status report for corrective actions; Annex K: Example of a non-conformance control implementing procedure; Annex L: Example of a corrective action request implementing procedure; Annex M: Example of an implementing procedure on tracking and trending of quality problems; Annex N: Example of a method of coding of non-conformance data for defect analysis; Annex O: Example of reports available from a defect analysis programme.