In order to qualify for Nonprofit USPS Marketing Mail prices, a nonprofit authorization with the Postal Service must be obtained by submitting PS Form 3624, Application to Mail at Nonprofit USPS Marketing Mail Prices, with supporting documentation.
For more information, see Publication 417, Nonprofit USPS Marketing Mail Eligibility: Nonprofit and Other Qualified Organization at https://pe.usps.com/text/pub417/welcome.htm, and DMM 703.1.0 at https://pe.usps.gov/text/dmm300/703.htm#ep1114977.