During a supplier audit, all of the following documentation can be reviewed EXCEPT

During a supplier audit, the auditor's access is limited to information relevant to the products or services being procured and the supplier's overall quality management system (QMS). Quality records for a product made for another customer are considered proprietary and confidential. Sharing such information would violate the supplier's confidentiality agreements with that customer. While an auditor must verify the QMS is effective, they must do so by reviewing records pertinent to their own organization's products or general system records, not by examining a competitor's or another client's specific data. This respects business ethics and confidentiality, a key principle in auditing.

A. Internal audit reports are a key indicator of the supplier's QMS maturity and self-correction capabilities, making them a valid area for review.
B. Parts inventory information is relevant for verifying controls like traceability, material handling, and management of nonconforming products.
D. Operating instructions are essential documents reviewed to ensure processes are defined, controlled, and followed as required by the QMS.

1. ISO 19011:2018, Guidelines for auditing management systems. Clause 4, "Principles of auditing," lists "Confidentiality – security of information" as a fundamental principle. It states, "Auditors should exercise discretion in the use and protection of information acquired in the course of their duties." This principle directly prohibits reviewing one customer's confidential records during an audit for another customer.

2. Russell, J. P. (Ed.). (2021). The ASQ Certified Quality Auditor Handbook (5th ed.). Chapter 11, "Supplier Management," discusses the relationship between customers and suppliers, which is governed by contracts and agreements that include confidentiality clauses. The handbook emphasizes that the audit scope must be respected, and access to proprietary information of third parties is typically excluded from this scope.

3. Goetsch, D. L., & Davis, S. B. (2020). Quality Management for Organizational Excellence (9th ed.). In the context of supplier partnerships and audits (Chapter 10), the text underscores the importance of trust and ethical conduct. Accessing a competitor's or another customer's proprietary data would be an ethical breach and destroy the trust essential for a supplier-customer relationship.

4. Purdue University, MET 44300 - Quality Control Courseware. Lectures on Supplier Quality Assurance emphasize that while auditors need access to evidence of a functioning quality system, this does not extend to proprietary information belonging to other clients. The audit's focus should be on the supplier's processes and records related to the auditing organization's products.