Consider using postage stamps to give your pieces more appeal. We can even customize a stamp for your mailing. If you are not using stamps, then a permit will need to be printed on your piece. You can add the permit to your file if your pieces are all mailing the same way. If you want extra pieces without permits or are mailing some pieces first class and some standard (bulk) then it would be best to have the permit added during the mailing process.
Standard (bulk) non-profit permit
First class permit
Permit No. 221