Due to a sharp increase in the number of listed companies and an increase in the amount and value of the traded shares at Tehran Stock Exchange (TSE), the segregation of trade activities from post -trade activities came to pass. In this regard and also considering the Islamic Republic of Iran's laws and regulations on the draft of securities market laws, steps for CSDI establishment were taken. Based on paragraph 7 of article 1 of the securities market law of the Islamic Republic of Iran in relation to registration, custody, and transfer of securities ownership, also the clearing and settlement of securities, Central Securities Depository of Iran (CSDI) was established. Also based on paragraph 5 of article 4 of the same law, the high council of stock exchange became liable for CSDI's activities. By September 2005, after the identity of its founders was clear and subscriptions of bank script on capital funds were paid and after the approval of the provisions, the registration of the company was accomplished and the managing director was appointed. The company became functional on December 26th, 2005 under registration number 262549.