Mailing Standards of the United States Postal Service Domestic Mail Manual > 100 Retail Mail Letters, Cards, Flats, and Parcels > 110 Retail MailPriority Mail Express > 114 Postage Payment Methods
Overview
1.0 Basic Standards for Postage Payment
Retail Priority Mail Express postage may be paid with adhesive stamps (see 604.1.0), postage evidencing systems (see 604.4.0), or with USPS Click-N-Ship. The mailer is responsible for proper payment of postage.
Any postage evidencing system may be used to prepay reply postage on Priority Mail Express shipments under 604.4.5.2.