Deciding on capital structure is one of the most challenging and vital decisions companies make to survive in a competitive market. Examining financing methods is one of the most important tasks of financial managers, which always affects the wealth and capital of shareholders. Usually, most companies start their activities with small capital and after being listed on the Tehran Stock Exchange, they need liquidity to develop their activities and implement development plans. In this case, companies issue new shares due to the limited credit of the banking system and the complexity of the process of obtaining a license to issue bonds. Now, considering that the companies listed on the stock exchange have a great tendency to increase capital and also the existence of various methods to increase capital, it was deemed necessary to conduct research on the methods of capital increase and their impact on stock returns.