A particular case that I have seen is fields for account numbers that expect X characters, but people are copypasting the numbers from sources where they are re

A particular case that I have seen is fields for account numbers that expect X characters, but people are copypasting the numbers from sources where they are represented with extra spaces for readability. (e.g. 1234 5678 instead of 12345678) And when they get to the validation, the last digit(s) have been lost.