1. Register public accounting firms that prepare audits.
2. Establish and/or adopt standards relating to the preparation of audit reports for issuers.
3. Conduct inspections of registered public accounting firms.
4. Conduct investigations and disciplinary proceedings.
5. Promote high professional standards and improve the quality of audit services offered by registered public accounting firms.
6. Enforce compliance with the Sarbanes-Oxley act (15 USC 7201, 2002).
Before the establishment of Sarbanes-Oxley and the PCAOB, there was no oversight board. Public accounting firms would perform "peer reviews" to verify that audits were being performed with due diligence. However, these reviews were not high priority, thus uncovering errors/negligence made by the public accounting firms by peers were rarely discovered. It was only after the massive failures of Enron and WorldCom that this gross negligence by the public accounting firm performing the audit came to light. It was clear that an independent review board was necessary to ensure due diligence is being followed when a public accounting
Cited: "Accountability in the Era of Global Markets." The Fletcher School. Feb. 2004: Tufts University Michaels, Adrian. "Accountants Urged to take Moral Stand." Financial Times. 19 Dec. 2004: Financial Time Limited