 What makes a mutual credit accounting system, into something like a money system is the contractual obligation of account holders to close all accounts at zero, which is to say, to depart the system neither owing nor owed.The credit theory of money says clearly that money does not need to be, or be backed by, commodities like gold.Mutual credit systems can perform, reasonably well, all of the three classical functions of money, as store of value, medium of exchange and unit of account.