Abstract: A heterogeneous stored-value system which offers interoperability among a number of proprietary payment card brands with differing fee structures. The system makes use of existing settlement practices and fee structures to increase the amount of commerce while imposing minimal changes. The benefits of the interoperability among different proprietary brands include reduced operating costs, since a single electronic cash pool can serve many different payment card brands. Although the electronic cash of the system is generic and is shared among the different payment card brands, the flow of electronic cash is prescribed in such a manner as to maintain an association between electronic cash (over the course of circulation) and the specific brand of payment card through which it was acquired by the customer. In this way, a transaction involving electronic cash represents a small piece of a much larger charge or debit transaction and carries its proportional share of the fees of the charge or debit transaction.