26 U.S. Code § 506 - Organizations required to notify Secretary of intent to operate under 501(c)(4)
An organization described in section 501(c)(4) shall, not later than 60 days after the organization is established, notify the Secretary (in such manner as the Secretary shall by regulation prescribe) that it is operating as such.
Not later than 60 days after receipt of such a notice, the Secretary shall send to the organization an acknowledgment of such receipt.
The Secretary may, for reasonable cause, extend the 60-day period described in subsection (a).
The Secretary shall impose a reasonable user fee for submission of the notice under subsection (a).
Upon request by an organization to be treated as an organization described in section 501(c)(4), the Secretary may issue a determination with respect to such treatment. Such request shall be treated for purposes of section 6104 as an application for exemption from taxation under section 501(a).