With the complexity of business in the modern world, the presence of major customers has made it easy to achieve the right returns for companies. On the other hand, the type of capital structure and cost management are effective in achieving this goal. Accordingly, in this study, the relationship between customers and capital structure of 124 companies that have been accepted and active in Tehran Stock Exchange for the period between 2011 and 2016 has been investigated. Literature and research backgrounds are collected through library studies and data are also available from the codall sites, www.rdis.ir, www.tse.ir, www.tse.tmc.com, and software transmissions New and data warehouse were compiled and analyzed for Ewiew's statistical software. Finally, the results indicate that there is no significant relationship between the cost of equity, the cost of debt and the overall structure of the capital with the concentration of customers.
