[gibspaulding]

> Developers make assumptions about postal codes

Until very recently I naively assumed that the area of a given zip code would be entirely within the area of some single city or town which would then be entirely within the area of a single county.

It was quite a rude awakening working with software that tries to apply the correct local taxes to a given address and finding that the statement “A given X can contain multiple Y” is true for every possible combination of zip, city, and county.