American zip codes have five digits, so that’s probably what you mean? Anyway, I agree, using the postal code for credit card authentication is insane. Some si

American zip codes have five digits, so that’s probably what you mean? Anyway, I agree, using the postal code for credit card authentication is insane. Some significant countries like UK and Canada use letters within these codes, so you can’t even assume that a credit card’s associated zip code can be entered with digits.