According to AU 230:  The auditor’s responsibility to exercise due care: “Due professional care requires the auditor to exercise professional skepticism. The auditor uses the knowledge, skill, and ability called for by the profession of public accounting to diligently perform, in good faith and with integrity, the gathering and objective evaluation of evidence. Under these guidelines, none of the answers suffice.

Under the AICPA code of professional conduct, the responsibility principle refers to maintaining public trust.

Under the AICPA code of professional conduct, the “scope and nature of services” principle requires that practitioners work in firms that maintain appropriate quality control procedures.

The General Standards Rule of the AICPA Code of Professional Conduct states that the auditor must have adequate technical training as an auditor.

A CPA must maintain objectivity and integrity in the performance of any professional service.

PCAOB procedures are to be obeyed for public company engagements. In addition to professional competence, there is due professional care, planning and supervision, and sufficient relevant data.

According to PCAOB guidelines:  “During the period of the professional engagement, a partner or professional employee of the firm, his or her immediate family, or any group of such persons acting together owned more than 5 percent of a client’s outstanding equity securities or other ownership interests.”

Under AICPA and PCAOB guidelines, independence is impaired by an employment arrangement with a client.  Under ET Section 100:  Participated on the attest engagement team or was an individual in a position to influence the attest engagement for the client when the attest engagement covers any period that includes his or her former employment or association with that client.”

Under PCAOB standards for public companies, an audit lead is required to rotate every five years.  The guidance provided by the PCAOB includes the following: “Auditors have many rigorous standards that must be upheld that are supposed to create independence from the companies they audit.   One of the most important is the mandatory lead rotation every five years.    This is a much more cost-effective way of increasing independence between auditors and clients.  When the lead auditor changes, they must “start from scratch” with their client, which means no longstanding relationship is intact.  In addition, the audit firm will have to spend less time on the audit than if it were an entirely new company, which saves massive amounts of time, and most importantly, money.”

SOX and SEC rules prohibit an accounting firm from auditing an issuer's financial statements if certain members of management of the issuer had been members of the firm's audit engagement team within the one year period preceding the beginning of audit procedures. These positions include CEO, CFO, and controller.