To get non profit postage rates you will need to get approval from the USPS and a non profit authorization number. Once you have this approval there are a few things that need to be done to ensure the piece qualifies for non profit rates
Return Address
The return address should be the exact same name and address registered under the non profit authorization. Any abbreviations are typically not accepted and should be approved prior to going to print.
Indicia or Stamp
A non profit mail piece should also have a non profit indicia or stamp. You do not need to have your own permit but the indicia will need to indicate that the mailing is non profit. Alternatively a specific non profit stamp may be used.
Postal Specs
The mail piece should also fall within USPS postal specifications to get the best non profit rates
The USPS has been strictly monitoring non profit mailings to ensure that people do not fraudulently use non profit rates. It is best to have a mail piece reviewed by a mailing professional prior to printing to ensure no changes need to be made to qualify for non profit rates.