Many of us think of money as a single number, $1 for example. As programmers, we often make the mistake of codifying that assumption in the way we store and build processes concerning money. If you haven't guessed yet, there is more to money than we'd expect. Similar to time, where a date is not a datetime is not a datetime with tzinfo, a float is not a Decimal is not a dollar is not a yen. We should always specify currency when recording, manipulating, or displaying money. We'll motivate this rule, and provide examples and some simple utilities to follow this rule effectively.