A PO Box address uses the box number instead of a street, followed by the post office's city, state and ZIP code. Large post offices often have ZIP codes reserved for their boxes, so a PO Box ZIP may differ from the ZIP of nearby homes.
How to write a PO Box address
JANE DOE
PO BOX 123
BOSTON MA 02205-0123Put “PO BOX” and the number on the delivery line, then the city, state and ZIP of the post office. Do not add a street address unless the post office has told you to.
Do PO Boxes have a street address?
Some post offices offer “street addressing,” which lets box holders use the post office's street address with the box number as a unit number so private carriers can deliver parcels. Availability depends on the office; the USPS PO Box page explains the service.
PO Box ZIP codes and ZIP+4
Within a box section, ZIP+4 extensions usually correspond to ranges of box numbers. The USPS ZIP Code Lookup returns the exact ZIP+4 for a box address; see ZIP+4 lookup.
Looking up a specific PO Box number
People often search a box number from a letter or bill, such as “PO Box 69703 Harrisburg PA.” A box number with a city and ZIP identifies where mail is collected, not who rents the box, and USPS does not publish box holders. To learn who uses a box, read the organisation name printed with the address, or contact the organisation through a phone number or website you find independently. The five digits after a box number are the ZIP code; look it up with the ZIP code lookup to see the post office's town.
Carriers and PO Boxes
Private carriers generally cannot deliver to a PO Box, because only USPS can access the box section. Merchants that ship by courier will ask for a street address instead; see FedEx and ZIP code searches.