The Big Four refers to the four largest public accounting firms. These firms are:
Deloitte & Touche
Ernst & Young (EY)
This group is the result of mergers amongst the prior Big Eight public accounting firms. These entities do not just provide auditing services. They also have a significant presence in other areas, including tax, consulting, actuarial, and legal services. Because of their broad geographical presence and high level of expertise, they provide most of the auditing work for the world’s publicly-held businesses.