Most associations are also tax-exempt entities, but they need not be. Because the requirements for federal income tax exemption are more stringent than those for nonprofit corporation status, there are some associations that are nonprofit corporations but do not qualify for exemption from federal income tax. However, these organizations are few and far between. Most nonprofit organizations qualify for federal income tax exemption under one of 25 subsections of Section 501(c) of the Internal Revenue Code. Most associations are tax-exempt under Sections 501(c)(3) or (c)(6), and a smaller number under Sections 501(c)(4) or (c)(5). In addition, some 501(c)(6) associations form related educational or charitable foundations exempt under Section 501(c)(3), along with other taxable and/or tax-exempt subsidiaries.