One of the advantages for employees in a group health plan is the contribution most employers make toward the cost of the health coverage premium â in many cases, employers pay one-half or more of the monthly premium for an employee.
The basic format consists of five decimal numerical digits. An extended ZIP+4 code, introduced in 1983, includes the five digits of the ZIP code, a hyphen, and four additional digits that determine a more specific location within a given ZIP code. The USPS provides a free online lookup tool for ZIP codes.
On July 1, 1963, the Post Office Department implemented the five-digit ZIP Code, which was placed after the state name in the last line of an address. To provide room for the ZIP Code, the Department issued two-letter abbreviations for all states and territories. Publication 59, Abbreviations for Use with ZIP Code, issued by the Department in October 1963, told why.