Mailing Standards of the United States Postal Service - Domestic Mail Manual > 200 Commercial Letters, Flats, and ParcelsDesignStandards > 230Commercial MailFirst-Class Mail > 234Postage Payment and Documentation
1.0 Basic Standards for Postage Payment
2.0 Postage Payment for Presorted and Automation Letters and Flats
3.0 Mailing Documentation
Postage for Presorted or automation First-Class Mail must be paid with affixed postage or permit imprint (604.4.0) as specified in 2.0. Residual letters (from presorted or automation mailings) with such postage may be eligible for the Metered Mail price.
First-Class Mail presorted and automation postage must be paid with postage evidencing system indicia, permit imprints, or precanceled stamps. All pieces in a mailing must be paid with the same method unless otherwise permitted by standard or Business Mailer Support authorization. Permit imprints may be used for mailings of nonidentical-weight pieces only if authorized by Business Mailer Support.
Unless permitted by other standards or authorization by Business Mailer Support, when precanceled postage or postage evidencing system indicia are used, only one payment method may be used in a mailing and each piece must bear the numerical value of postage under one of these conditions:
Where it is not practicable for the mailer to affix the exact postage to each piece or to affix the lowest postage price to all pieces in the mailing, the mailer may compute postage for the mailing as if the lowest price affixed to any piece in the mailing were affixed to all pieces. Additional postage is computed based on the difference between the lowest price affixed to any piece in the mailing and the price for each price level in the mailing. This computation must be documented to meet the basic standards in 3.0. No refund is paid for any piece where postage is affixed at a price higher than the lowest price claimed for or affixed to any piece. The total additional postage must be paid either by advance deposit account or by a meter stamp affixed to the back of the accompanying postage statement.
See 203.1.0 and 203.2.0 for postage statement and documentation standards.