501(c)(4)
(US LAW) tax-exempt nonprofit as defined under Treasury Code section 503(c)(4). Very similar to a 501(c)(3), but while a 501(c)(3) is more completely exempt from taxes, a 501(c)(4) has more leeway in what sorts of political activities it may engage in.
For example, a 501(c)(4) organization may explicitly endorse a ballot position or candidate, whereas a 501(c)(3) may not.
For example, a 501(c)(4) organization may explicitly endorse a ballot position or candidate, whereas a 501(c)(3) may not.
There are many examples of 501(c)(3) organizations paired with 501(c)(4) organizations. This arrangement is known as the "Sibling Option" and is used by the Koch Family Foundations for funding Tea Bag political associations.