Bait money or bait bills are used by banks to aid the tracing of bank robbers.
Bait bills are bills whose serial number is recorded by the bank either by making a copy or by listing in a log book. During a bank robbery, if a robber has taken the bait money, details of this can be passed on to the police. If the money is found in the possession of someone, or used to purchase goods, this can make it easier to find the perpetrator of the bank robbery. When the bait money has left the bank it is known as hot money.