IIA guidance emphasizes conflict of interest checks in the hiring process for CAEs to ensure the integrity and independence of the internal audit function. Functional reporting to the board or similar oversight is also a standard recommendation but not a hiring precondition.

If the engagement supervisor accepts an expensive gift from management after the issuance of a final audit report, it violates The IIA's Code of Ethics principle of objectivity. Objectivity requires auditors to maintain an unbiased mental attitude and avoid conflicts of interest or unduly influenced behaviors. Accepting gifts can compromise the perceived or actual independence of the auditor, influencing decisions or outcomes of audits in favor of the gift giver.
The IIA's Code of Ethics on Objectivity.

The primary responsibility of the internal audit activity within a risk and control framework is to verify that management has met its responsibility for implementing effective controls. This aligns with the IIA's definition of the internal audit function's role, which is to provide independent and objective assurance that an organization's risk management, governance, and internal control processes are operating effectively.
The Institute of Internal Auditors (IIA) - International Standards for the Professional Practice of Internal Auditing.

To promote the independence of the internal audit activity, it is required that the chief audit executive reports functionally to the board. This structural alignment helps ensure that the internal audit function is not unduly influenced by management, which might be the subject of audits, and can freely report on its findings and recommendations without fear of reprisal.
The IIA's International Standards for the Professional Practice of Internal Auditing on independence and objectivity.

The internal audit charter is a formal document that defines the internal audit activity ' s purpose, authority, and responsibility. According to IIA standards, the internal audit charter must define the reporting relationships within the organization, which facilitates the independence and objectivity of the internal audit function. The inclusion of reporting relationships ensures that there is clear communication and understanding regarding the internal audit activity's position within the organization.
IIA Standard 1000: " Purpose, Authority, and Responsibility "