The float is the money in the banking system that exists in the time between when a check or withdrawal is initiated and when it clears. It creates interesting challenges for counting the money supply: if Employer A writes Person B a check for $100, Person B’s bank account value will go up by $100 immediately, but there’s often a time lag until Employer A’s bank account has officially lost the $100. In the US, this time period is usually less than one day.