ZIP and postal codes

• What is a ZIP+4 code and how do you find yours?

  A ZIP+4 adds four digits to a 5-digit ZIP code to pinpoint a delivery segment such as a city block, building or PO box. What the digits mean, how to find yours and whether you need it.

• ZIP codes vs ZCTAs: why free lists never match

  ZIP codes and Census ZCTAs look alike but are different things. Here is why free ZIP code lists disagree, and what that means for you.