business reply

noun

1. a form of mail, as a postcard, letter, or envelope, usually sent as an enclosure, and which can be mailed back by respondents without their having to pay postage.

Example Sentences

Ferry, Columbia and Wahkiakum counties discovered it was cheaper to affix first-class mail stamps to ballot envelopes, while the other 36 counties are using business reply postage.

From Seattle Times