Editing Postal code (section)

==== United States ====
{{further|ZIP Code}}

In the United States, the basic [[ZIP Code]] is composed of five digits. The first three digits identify a specific [[sectional center facility]]—or central sorting facility—that serves a geographic region (typically a large part of a state). The next two digits identify a specific post office either serving an area of a city (if in an urban area or large suburban area) or an entire village, town, or small city and its surrounding area (if in a small suburban or rural area).

There is an extended format of the ZIP Code known as the [[ZIP+4]], which contains the basic five-digit ZIP Code, followed by a hyphen and four additional digits. These digits identify a specific delivery route, such as one side of a building, a group of apartments, or several floors of a large office building. Although using the ZIP+4 offers higher accuracy, addressing redundancy, and sorting efficiency within the [[USPS]], it is optional and not widely used by the general public. It is primarily only used by business mailers.

For high volume business mailers using automated mailing machines, the USPS has promulgated the [[Intelligent Mail barcode]] standard, which is a barcode containing the ZIP+4 code plus a two digit [[delivery point]]. This 11-digit number is theoretically a unique identifier for every address in the country.