ZIP+4 ZIP Code Data Background and Information

What do the last four digits of a nine-digit ZIP code mean? Why are these digits useful?

When the US government created the Zoning Improvement Plan codes during World War II they only had five digits. As mail delivery needed to become more exact, the USPS realized that the 5-digit ZIP code did not divide the regions up into small enough sections. In 1983, the postal service introduced ZIP+4 codes. A ZIP+4 code has the original five-digit ZIP code, but it also adds a four digit code which identifies a specific geographic segment, such as a block of homes, a post office box, an apartment complex, or a business.

This is an example of some ZIP+4 data in Beverly Hills, CA (ZIP Code 90210 of course).

ZIP Code	+4 Code	City	Street
90210	4000	Beverly Hills	Palm Drive
90210	4001	Beverly Hills	Beverly Blvd
90210	4002	Beverly Hills	Beverly Blvd
90210	4003	Beverly Hills	Doheny Dr
90210	4004	Beverly Hills	Oakhurst Dr
90210	4005	Beverly Hills	Oakhurst Dr

ZIP+4 data is available for people who would like to use the ZIP+4 codes. The USPS website has a ZIP+4 lookup on it. You can also purchase complete databases at affordable prices from ZIP code database providers.

The plus-four code is not required in most circumstances, but it can greatly improve the delivery of your mail. If ZIP+4 data is not included on a piece of mail, the post office uses a machine which determined the +4 code using the address and prints a barcode on the mail.