Activity of the credit union consists of organizing mutual financial assistance by meeting the needs of its members in the services of saving and obtaining loans. Is necessary that all shareholders of the credit union were members of a single community, would know each other well enough to enjoy mutual trust. Until the 70's there was a proliferation of the U.S. credit unions due to the increase of their number and the number of shareholders, although it must be acknowledged that there was also and a qualitative growth. The relationship of shareholders with credit union are not client-based, they are co-operative, based on different principles and standards, in particular, on the principles of the law of obligations.