To use a permit imprint, the pieces must be of identical weight and, unless all the pieces are in a weight category for which the price does not vary by zone, the pieces must be separated by zone when presented to the Post Office, except under 2.2.
A permit imprint may be used for mailings of nonidentical-weight pieces only if authorized by Business Acceptance Solutions at USPS Headquarters (see 608.8.0 for address).