While internal auditors are hired directly by their company, they can achieve independence through their reporting relationships. Independence and objectivity are a cornerstone of the IIA professional standards; and are discussed at length in the standards and the supporting practice guides and practice advisories. Professional internal auditors are mandated by the IIA standards to be independent of the business activities they audit. This independence and objectivity are achieved through the organizational placement and reporting lines of the internal audit department. Internal auditors of publicly traded companies in the United States are required to report functionally to the board of directors directly, or a sub-committee of the board of directors (typically the audit committee), and not to management except for administrative purposes.