A 501(c) organization, also known colloquially as a 501(c), is a tax-exempt nonprofit organization in the United States. Section 501(c) of the United States Internal Revenue Code  provides that 29 types of nonprofit organizations are exempt from some federal income taxes. Sections 503 through 505 set out the requirements for attaining such exemptions. Many states refer to Section 501(c) for definitions of organizations exempt from state taxation as well. 501(c) organizations can receive unlimited contributions from individuals, corporations, and unions.