According to the United States Postal Service, Business Reply Mail is a postage permit businesses can affix to reply cards or envelopes for their customers, allowing the businesses to pay only for the postage used. When a customer replies using a prepaid Business Reply Mail envelope, the Postal Service tallies the number of responses and then sends the company a bill to cover the cost.
Business Reply Mail envelopes have advantages over prepaid postage because a business does not have to incur an upfront cost, other than the annual BRM fee, to provide a reply service to its customers. A popular urban legend encourages people to affix the Business Reply labels they receive in unwanted junk mail to heavy objects and return them in the post, ostensibly to charge the company that sent the junk mail extra postage fees. However, Business Reply envelopes and labels cannot be used for the purposes other than those indicated by the company, and the Postal Service will simply discard any nonstandard items that consumers attempt to mail using these labels. Business Reply labels also cannot be altered to allow consumers to send mail wherever they want for free, as the prepaid code is tied directly to the company that issued the postage.