Abstract: The priority in subscription of new shares is the same as priority given to the previous shareholders that is under certain legal procedures and nature. The source of priority in Iranian law is law and articles of association in American law. In both legal systems, priority is a transactable right. The transfer of this right is carried out in the stock market or outside the market and based on restrictions the shareholders face in transfer of their shares. Like movable properties, priority can be attached by the third party and it can be sold on tender without formalities and immediately after the approval of the court. In Iranian law, priority is a peremptory norm and a non-abrogatable right of the former business partners. According to the articles of association, their rights cannot be denied although denying their priority is within the discretion and authority of extraordinary general assembly, which should be well-justified and non-forceable. The procedures must be brought in the reports of the board of directors and the official inspectors for proper decision making. In the United States of America’s law, however, the priority is a complementary principle and the shareholders will enjoy priority in case it has already been mentioned in the articles of association of the bank or financial institutions, otherwise, they will have no priority in subscription for new shares or for capital increase unless the articles of association is amended.