An Expert system solves problems that are normally solved by human experts. We believe that SERAPEUM is even better in the sense that the speed of responses is unmatched by a human being. An expert system consists of a knowledge base of the domain, in our case tax law that draws both from public databases or private, reasoning mechanisms to apply knowledge to problems that are proposed mechanisms to explain the users the reasoning used when providing a response and mechanisms of learning and acquiring new knowledge. SERAPEUM also provides references to information that is based (whether Judgments, Legislation and Consultations resolved by the Director General). To create a knowledge base is necessary to have at least one human expert's domain. In our case has been formed through questionnaires and experience accumulated over time of various professionals in tax law.