A complete address according to the USPS - Address must include:
- Intended recipients name or other designation.
- Delivery address (including street number and name (predirectional, suffix, and postdirectional as appropriate), post office box number, rural or highway contract route and box number), and secondary descriptor and number (e.g., suite or apartment number, floor) if needed.
- City and state.
- ZIP Code or ZIP+4 code where required.
The address must be sufficiently complete to enable matching the current USPS ZIP+4 file when using current CASS-certified address matching software. Standardized address elements are not required.
A return address tells the USPS where the sender wants the mail returned if it is undeliverable.
A return address is required on certain types of mail. Preferred return address placement is the upper left portion of the mailpiece or the upper left part of the address area—on the side of the piece bearing postage. Mail qualifying for Nonprofit Standard Mail prices must have the name and return address of the authorized nonprofit organization either on the outside of the mailpiece or in a prominent location on the material being mailed (inside the mailpiece).
The following guidelines for addressing a mailpiece are outlined in USPS Postal Addressing Standards:
- Use simple sans serif type with uniform stroke thickness.
- Type or machine-print in dark ink on a light background with a uniform left margin.
- Left-justify every line in the address block.
- Use two-letter state abbreviations.
- Use one space between city and state, two spaces between state and ZIP+4 code.
- Use appropriate ZIP+4 code (if unknown, use 5-digit ZIP Code).
- A minimum of 8-point type, or if the mailpiece bears a POSTNET or Intelligent Mail Barcode with a delivery point routing code, a minimum of 6-point type is acceptable if printed in all capital letters.