– CR(tm) Certificate of Mailing PS Form 3817
In Reply To
https://about.usps.com/forms/ps3817.pdfPostal Operations Manual Hand-Book231.4 Hand-Back and Mail-Back Service
Postmarks rather than other obliterations should be used to provide the following services whenever they are available:
a. Hand-Back Service
(1) When a customer personally presents an addressed or unaddressed envelope, postal card, or other item described in 231.63 to a postal clerk for cancellation with the current day's postmark, the Post Office must postmark the item and return it, or hand it back, to the customer. ....
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