The postal abbreviation for the state of Washington is "WA." The state actually has two accepted abbreviations: a postal service abbreviation and a standard abbreviation. The standard abbreviation for the state of Washington is "Wash."
All postal abbreviations consist of two letters, both of which are capitalized, with no period following the letters. Standard abbreviations are often used in written documents in the place of the longer state name. The standard abbreviation is frequently a shortened version of the state name starting with a capital letter followed by lower case letters and ending with a period. The postal code abbreviation is preferable in addresses that contain zip codes, but the standard abbreviation appears most other times an abbreviation is used.