The Building Societies Association is a trade association, representing mutual lenders and deposit takers in the UK including all UK building societies. There are 52 mutual lenders and deposit takers in the UK including 47 building societies. Mutual lenders and deposit takers have total assets of over £375 bn and, together with their subsidiaries, hold residential mortgages of almost £235 bn, 19% of the total outstanding in the UK. They hold over £250bn of retail deposits, accounting for 22% of all such deposits in the UK. Mutual deposit takers account for about 34% of cash ISA balances. They employ approximately 50,000 full and part-time staff and operate through approximately 2,000 branches.

The BSA was established in 1869. It has two principal functions - to act as the central representative body for building societies and other mutual lenders and deposit takers and to provide information to its members. The BSA puts forward the industry view to government, parliament, regulators, the media and other interested bodies. It also provides information and advice to building societies on a range of relevant subjects.

There was substantial change in the building society sector in the mid to late 1990s, with a number of large societies giving up their mutual status and becoming banks, owned by shareholders. Mutual societies have only the interests of their member-customers to consider and have no shareholders to whom they need to pay dividends. Paying dividends generally adds about 35% to the overall costs of running a savings and mortgage business. Generally, this means that committed mutual building societies can offer more competitive rates of interest on mortgage and savings products.

The BSA offers advice and assistance on the whole range of issues affecting the operation of building societies. The BSA is not a regulator - that is the role of the Financial Services Authority, nor does it deal with complaints about building societies - which are looked after by the Financial Ombudsman Service, if they cannot be resolved by the society itself.