GLOSSARY
Ancillary service endorsement
By Justin Winter · Updated August 28, 2026
A printed instruction on a mailpiece telling USPS what to do if it cannot be delivered as addressed — return it, forward it, or report the new address.
Endorsements such as "Return Service Requested" or "Address Service Requested" appear near the address block. They select, in advance, the treatment an undeliverable piece receives and whether the sender is told what happened.
Without an endorsement the default handling for the class applies, which can mean the piece is disposed of and you never learn the address was bad.
See also
- Return to sender — A mailpiece sent back to the sender because it could not be delivered, was refused, or went unclaimed.
- Undeliverable as addressed — USPS’s classification for a piece that cannot be delivered to the address written on it — the umbrella term behind most returned mail.
- Change of address — The USPS request that forwards mail from an old address to a new one for a limited period after a move.
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