The number of shareholders of a credit union is limited and formalized by a list. Limit of the number is defined by the assembly and such assembly establishes the charter. Specialization of credit unions to provide financial services to its shareholders requires a particularly strict regulation of membership and acceptable activities. Among the U.S. credit unions, there are three groups that differ in terms of assets, shareholders, and business services. Cooperation between credit unions, how they would not have been named, took place always, from the moment when the movement moved outside one credit union. A potential new member of a credit union must submit a recommendation of shareholders in which the referee becomes a warrant of a future member of the credit union. Over 30% of the assets of credit unions are investments in government securities, certificates of deposit of banks and savings loan associations, as well as in the parent credit unions, and other risk-free investments. Credit unions of the open type are still controlled by their members, but at the same time provide services to people who are not its members (external customers). The value of credit unions is not limited to the role of the economic agent - they are an important element of the social structure and a factor of social stability and progress. To increase the number of credit unions in 1979 was adopted the corresponding law that serves as the legal basis of their activity.