Nunavut (created in 1999) does not have a designated abbreviation because it did not exist when these codes were phased out, though some can be found in other official works.
For Quebec and New Brunswick, the two provinces with large numbers of French speakers, the initials in both languages are identical.
The policy of not overlapping adjacent-country abbreviations, which helps the postal processing system avoid dealing with naming collisions, precludes use of NV for Nunavut (compare NV for Nevada) and TN for Terre-Neuve/Terra Nova/Newfoundland (compare TN for Tennessee).
[8] The USPS changed the abbreviation for the U.S. state of Nebraska from NB to NE in November 1969 to avoid a conflict with New Brunswick.
[9] The Canadian policy of adopting provincial abbreviations that did not overlap with the state abbreviations of adjacent countries differed from the situation in Mexico, where two-letter combinations for Mexican states were chosen by various competing commercial organizations (in the absence of any official Correos de México list) regardless of whether that combination was already in use in the United States or Canada, e.g., CO (Coahuila/Colorado), ME (Mexico/Maine), MI (Michoacán/Michigan), MO (Morelos/Missouri), NL (Nuevo León/Newfoundland and Labrador), and BC (Baja California/British Columbia).
[11][12][13][14] The last line of the address block area should include only the complete country name (no abbreviations) written in uppercase letters.
Mail to the US often omits the country name, and vice versa, given that no postal codes nor provincial/territorial/state abbreviations duplicate one another.
From the USPS IMM 122.1 Destination address Within and to Canada, there must be two spaces between the province abbreviation and the postal code, as shown below between "ON" and "K1A 0B1":