According to the IIA's guidelines, the internal audit charter should clearly define the internal audit activity's position within the organization. This is essential to establish the authority and scope of the internal audit function, ensuring that it has the necessary independence and resources to fulfill its duties effectively.
The Institute of Internal Auditors (IIA) guidelines on internal audit charter.

In consulting engagements, the needs and expectations of the engagement client are a greater consideration compared to assurance engagements. This is because consulting engagements are typically more advisory in nature and specifically tailored to provide value and improve an organization's operations based on the client's requirements. In assurance engagements, the focus is more on the independent assessment against criteria or standards, which does not vary based on client needs to the same extent.
IIA Practice Advisory on Consulting Services

According to IIA guidance, the internal audit activity can participate in and provide consulting services that add value and improve an organization's operations. By assisting the committee and consulting with management on the organization's responses and control activities, the internal audit activity utilizes its expertise in risk management while maintaining its advisory role without compromising its independence or objectivity.
Institute of Internal Auditors (IIA) - International Professional Practices Framework (IPPF)

According to IIA guidance, the internal audit activity should refrain from conducting an assurance engagement for which it lacks the necessary competencies or skills. This requirement ensures that internal audits are carried out effectively and that audit conclusions are reliable. It upholds the integrity and professionalism of the internal audit function by ensuring that all engagements are performed with the requisite level of expertise.
The IIA's International Standards for the Professional Practice of Internal Auditing on proficiency and due professional care.

Policies that provide examples of inappropriate business relationships best promote objectivity in the internal audit activity's work by explicitly defining what constitutes a conflict of interest and guiding auditors on how to avoid situations that might impair their objectivity. This clear delineation helps maintain the independence and unbiased perspective necessary for effective auditing.
Institute of Internal Auditors (IIA) - Code of Ethics and Professional Standards; literature on maintaining objectivity in internal auditing.