Collateralized mortgage obligations are derivatives securities based on mortgage loans which issued in different maturities, interest rates and credit ratings. In Iran attention to decision authorities for the first time allowed Iran Melli bank and Maskan bank to issue this kind of securities. One of the main questions in issuing this kind of securities is maximizing the issuer profit by choosing optimum maturity, number and size of each trench.
In this paper by using combination of dynamic programming approach and Monte Carlo simulation technique we maximize the profit of issuer by optimizing the maturity of mortgage backed securities (reduce in issuing cost). Considering 3 trenches and up to 8 years maturity with 12% average rate of pool of mortgages, the result of the model determines the maturity of 4, 8 and 3 years respectively for first, second and third trenches. Compared with the proposed 5-years and non-classified mortgages, dynamic programming model leads to rise 1.2% in profit of issuer.