A return address is an important part of any mail piece. For some types of mailings, it is a required element of the mailing panel, and in general it is a good idea because it allows the USPS to notify the mailer of address correction for first class mail (single-piece and presorted).

Return address legibility is crucial, especially since some letter mail may be redirected to the return address by PARS (Postal Automated Redirection System) if the mail piece is undeliverable as addressed.

The preferred location for a return address is the upper left corner of the mail piece or the upper left corner of the addressing area. If there is a secondary address element (apartment number, suite number, etc.) that must be included on the street address line.

If postage is paid using precanceled stamps or a company permit imprint (indicia), the return address must include the 5-digit or 9-digit ZIP code. ZIP codes must also be used in the return address on all official mail (penalty mail) and on periodicals mail when Address Service Requested is specified on the mail piece.

Here are the situations when a return address must be used;

• Any class of mail endorsed with an ancillary service request (i.e., return service, forward service, address service, forward service)
• Official mail
• Mail using precanceled stamps as postage
• Mail using a company permit imprint for postage
• Priority Mail
• Periodicals mailed in envelopes or wrappers and periodicals endorsed with address service requested
• Package services, except for unendorsed bound printed matter
• Registered mail
• Insured mail
• Collect on Delivery (COD)
• Certified mail if a return receipt is requested
• Express mail if a return receipt is requested
• Detached address labels (DALs)