Comprehensive and Detailed In-Depth Explanation:

Once a Stage 2 certification audit has commenced, certain logistical or planning-related elements may still be adjusted, while others are fixed by prior agreement and cannot be changed.

✅ C. Audit Plan:

The audit plan is a document that outlines the scope, objectives, criteria, and logistics of the audit. According to ISO/IEC 17021-1:2015 (the standard for bodies providing audit and certification of management systems), clause 9.2.3.3 allows for modification of the audit plan based on real-time conditions during the audit — such as availability of auditees or changes in process access.

✅ F. Increase of Audit Duration:

Audit duration is generally determined during audit planning based on factors like employee count, risk, complexity, etc. However, if during Stage 2 it is found that more time is needed (e.g., due to additional processes, scope not fully covered, or significant findings), auditors are permitted to extend the audit. This ensures full coverage of all required areas as per ISO/IEC 17021-1 clause 9.1.4 and IAF MD 5.

❌ A. Agreed Language of the Audit:

This is determined and agreed upon in the contract and audit planning stages. Changing it during Stage 2 would create communication and documentation issues, especially in multi-site or multi-national audits.

❌ B. Audit Scope:

The audit scope is defined in the contract and certification agreement based on clause 4.3 of ISO 9001:2015. Changing it mid-audit would invalidate planning, required competencies, and potentially even the certification basis.

❌ D. Agreed Standard for the Audit Criteria:

Changing the standard (e.g., from ISO 9001 to ISO 13485) is fundamentally altering the purpose and contractual basis of the audit and is not permissible once Stage 2 has started.

❌ E. Audit Checklist:

The checklist is a tool prepared by the auditor as part of audit preparation and is based on the audit plan and standard requirements. While it may be adapted during the audit (e.g., if new risks arise), it does not constitute a formal change like duration or scope.

Relevant References:

ISO/IEC 17021-1:2015 Clause 9.2.3.3 (Audit Plan Modification)

IAF MD 5:2019 (Duration of QMS Audits)

ISO 9001:2015 Clause 4.3 (Scope of the QMS)

ISO/IEC 17021-1:2015 Clause 9.1.4 (Audit Duration)