Nationwide are a building society, governed by the UK Building Societies Act 1986, and regulated by the Financial Services Authority.

They are the largest building society in the United Kingdom in terms of total assets. The company's core business is providing personal financial services.

As a mutual organisation, Nationwide are owned by and managed for the benefit of its members - their retail savings and residential mortgage customers - rather than for shareholders.

The company's main focus is serving their members' interests while retaining sufficient profit to increase and further develop their business and meet regulatory requirements. They return value to their members by offering typically higher interest rates on savings and lower interest rates on loans than those offered by their main competitors. This returned value is commonly referred to as their member value. As a result of returning value to its members, the company earns lower pre-tax profits than its main competitors (typically banks or other non-mutual organisations).