<P> In 1983 , the U.S. Postal Service introduced an expanded ZIP Code system that it called ZIP + 4 , often called `` plus - four codes '' , `` add - on codes '' , or `` add - ons '' . A ZIP + 4 Code uses the basic five - digit code plus four additional digits to identify a geographic segment within the five - digit delivery area , such as a city block , a group of apartments , an individual high - volume receiver of mail , a post office box , or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery . But initial attempts to promote universal use of the new format met with public resistance and today the plus - four code is not required . In general , mail is read by a multiline optical character reader ( MLOCR ) that almost instantly determines the correct ZIP + 4 Code from the address -- along with the even more specific delivery point -- and sprays an Intelligent Mail barcode ( IM ) on the face of the mail piece that corresponds to 11 digits -- nine for the ZIP + 4 Code and two for the delivery point . </P>
<P> In 1983 , the U.S. Postal Service introduced an expanded ZIP Code system that it called ZIP + 4 , often called `` plus - four codes '' , `` add - on codes '' , or `` add - ons '' . A ZIP + 4 Code uses the basic five - digit code plus four additional digits to identify a geographic segment within the five - digit delivery area , such as a city block , a group of apartments , an individual high - volume receiver of mail , a post office box , or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery . But initial attempts to promote universal use of the new format met with public resistance and today the plus - four code is not required . In general , mail is read by a multiline optical character reader ( MLOCR ) that almost instantly determines the correct ZIP + 4 Code from the address -- along with the even more specific delivery point -- and sprays an Intelligent Mail barcode ( IM ) on the face of the mail piece that corresponds to 11 digits -- nine for the ZIP + 4 Code and two for the delivery point . </P>
what is the last 4 digits of a zip code called
what is the last 4 digits of a zip code called
plus - four codes add - on codes add - ons
plus - four codes add - on codes add - ons