Postal Explorer >
Mailing Standards of the United States Postal Service, International Mail Manual >
4 Treatment of Outbound Mail > 420 Unpaid and Shortpaid Mail > 422 Unpaid Mail
Regardless of mail class, return to the sender each unpaid mailpiece that has a return address. Endorse the mailpiece with rubber stamp R-1300-230, Return For…Additional Postage.
Regardless of mail class, forward each unpaid mailpiece that does not have a return address to the Mail Recovery Center for proper disposition.