Perform a ZIP+4 code lookup by entering the full address into the United States Post Office’s Look Up a ZIP Code tool. The tool also allows entering a ZIP+4 code into the box to find an address in standard USPS formatting.
The Post Office began using postal district or zone numbers in large cities during World War II. In 1963, it introduced the five-digit ZIP code along with the two-letter state abbreviations to ensure addresses with the ZIP code would continue to fit onto magazine mailing labels. In 1967, the USPS began requiring the use of the abbreviations and ZIP codes for second and third class mail.
In 1983, the USPS introduced the ZIP+4 codes. There was initial resistance and the postal service offered discounts for large volume mailers in 1983. However, the public resistance was so great that the USPS does not require the use of the additional four digits.
While the addition of the four digits usually indicates an individual mailbox, there are exceptions. As of 2015, the USPS uses a digital optical scanner that reads the address and imprints an 11-digit bar code on each piece of mail that indicates a particular mail delivery point. The 11 digits include the nine digits for the ZIP+4 along with two additional numbers for the delivery point.