In an audit firm, the policies and procedures of quality control must be designed to prepare the audit firm and its staff to comply with relevant ethical requirements (see the figure below).

One of the ethical requirements refers to the Code of Ethics for Professional Accountants prepared by International Ethics Standards Board for Accountants (IESBA). All members of the accounting and auditing profession must adopt the following fundamental principles of ethics (IESBA 100.5).
Integrity: to be straightforward and honest in all professional and business relationships
Objectivity: not to allow bias, conflict of interest or undue influence of others to override professional or business judgments.
Professional competence and due care: to maintain professional knowledge and skill at the level required to ensure that a client firm receives competent professional service based on current developments in practice, legislation and techniques and act diligently in accordance with applicable technical and professional standards.
Confidentiality: to respect the confidentiality of information acquired as a result of professional and business relationships, and therefore, not disclose any such information to third parties without proper and specific authority, unless there is a legal or professional right or duty to disclose, nor use the information for his/her personal advantage or for the advantage of third parties.
Professional behavior: to comply with relevant law and regulations and avoid any action that discredits the accounting and auditing profession.
Independence: In addition to these fundamental principles of ethics, an auditor must also maintain independence in planning, performing the audit and determining his/her audit opinion. In this context, independence includes both independence of mind and independence in appearance. Independence of mind is the state of mind that permits the expression of a conclusion without being affected by influences that compromise professional judgment, and thereby allowing an individual to act with integrity and exercise objectivity and professional skepticism. Independence in appearance: the avoidance of facts and circumstances that are so significant that a reasonable and informed third party would be likely to conclude, weighting all the specific facts and circumstances, that a firm’s or a member of the audit team’s, integrity, objectivity or professional skepticism has been compromised.