The emergence of forex margin trading transactions or foreign exchange trading in indonesia is increasingly popular. Begins with an agreement between a potential investor and a company broker / company broker representative, which includes an agreement to make a purchase and sale of forex. In practice, many actions are found that are not in accordance with the agreement made by the broker, causing losses for investors or defaults. Therefore, the legal consequences of default and the causes of default are the focus of research. Based on this research, several problems were found as follows: why is there a default on brokerage companies in forex margin trading transactions in the futures exchange? What are the legal consequences of default by brokerage companies in forex margin trading transactions? This research is normative legal research. Legislative approach, case approach, conceptual approach. The results of this study indicate that the causes of default are technological engineering, disclosure of information on brokerage representatives of companies, affiliation of companies with futures traders. Keywords : tort, forex, futures trading