One I always enjoyed that's not on the list (because it's UK specific, I guess) is: Buildings don't have multiple postcodes in different outcodes ( https://en.

One I always enjoyed that's not on the list (because it's UK specific, I guess) is: Buildings don't have multiple postcodes in different outcodes ( https://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdom#Outward_code https://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdo... ). Counter example: * Merchant Venturers building, Woodland Road, Bristol BS8 1UB * Merchant Venturers building, Park Row, Bristol BS1 5UB