The “commercial paper discount” is one of the common ways of financing in the world banking. Because some objections and religious doubts, the using of these method in Islamic banking is faced with challenges. So, definition of the nature of the commercial paper discount is important for determine the effects, terms and conditions governing its.In this study, different religious jurisprudence opinions and legal doctrines about nature of the commercial papers discount has been criticized and analyzed, comprehensive approach, this article provide a comprehensive analysis of the nature of commercial paper discount in the banking system, according to the commercial description of these documents, and with regard to banking regulations and guidelines, and study its conditions and terms.ultimately, we can conclude that the commercial paper discount, in Islamic Banking, is analyzed in the form of a “Debt Purchase” agreement. This analysis is consistent with the true nature of the discount in the banking system, as well as the nature of commercial paper and its regulation. In the other hand, it is also consistent with famous Shiite jurists opinions.