Mailing Standards of the United States Postal Service - Domestic Mail Manual > 100 Retail Mail Letters, Cards, Flats, and Parcels > 170 Retail MailMedia Mail and Library Mail > 174 Postage Payment and Documentation
1.0 Postage Payment Methods for Media Mail and Library Mail
2.0 Postage Paid With Permit Imprint
The mailer is responsible for proper postage payment. Subject to the corresponding standards, postage for Media Mail and Library Mail may be paid by any method (see 604) except precanceled stamps.
In a postage-affixed single-piece mailing, the mailer must apply enough value in adhesive stamps or meter stamps equal to the postage required.
A mailer may mail material without affixing postage when payment is made at the time of mailing from a permit imprint advance deposit account established with the USPS under 604.5.0.