A building society is a mutual organisation owned by its members - its savers and borrowers - and not by shareholders. Its traditional purpose was to lend money to individuals to purchase or remortgage their homes. This money used to come exclusively from individual saving members who are paid interest on their deposits. Now, an increasing proportion, but still a minority of the funds, is raised on the commercial money markets.
Since the early 1980s there has been a progressive relaxation of the rules governing the sources from which building societies may raise money for lending. It was an attempt to allow societies to compete more effectively with banks and other specialised lenders.