The members make a list of services they can offer and those they might require. They are then interviewed and provide letters of reference. Every hour of service earns the member a credit unit. All services are treated equally. Participants buy services they need with the units they have earned. Hours of supply and demand are balanced in a data bank. Many Time Banks give their members a «deposit book» recording all their transactions. Participants can donate credit units to others or deposit them in a «joint account.»