In postal mail, a return address is an explicit inclusion of the address of the person sending the message. It provides the recipient (and sometimes authorized intermediaries) with a means to determine how to respond to the sender of the message if needed.
The return address need not include a sender's name, but should include address or P.O. box details in the same way as the delivery address should. In some countries, the return address is conventionally located in the upper left hand corner of the envelope, card, or label. In the United Kingdom, the return address is usually placed on the reverse of the envelope, near the top.
Businesses often use envelopes preprinted with a return address. Many individuals have sheets of adhesive labels preprinted with their home address to affix to their correspondence. Charities sometimes include such sheets in mailshots. Rolls of Return Address Labels can be purchased from companies that sell personalized labels to provide individuals an easy way to peel and stick return address labels to their envelopes.
The return address is not required on postal mail. However, lack of a return address prevents the postal service from being able to return the item if it proves undeliverable; such as from damage, postage due, or invalid destination. Such mail may thus become dead letter mail.
Should the return address be of a different state or country, the mail may be routed through that location for ease of return.