Purchase of debt is one of the disputed entity in Imamiite jurisprudence and frequently practical in banking transaction. Thedisputes are about substance, position and variations. In international legal systems, This entity are comparable whitForfeiting(that is an international legal entity that could be similar to purchase of monetary debt),Factoring(that is an international entity and could be similar to purchase of monetary debt in general and absolute meaning) , Mortgage Backed Securities and AssetBacked  Securities and its function in banking system aresimply conceivable by comparing it with purchase of debt in Iranian law. The purpose of this paper isanswering to this question that whether the legal and jurisprudence challenge by interest(purchase of monetary debt) are justifiable. Because this entity have been entered into Iranian legal literature and its executive guidelines are adopted by Money and Credit Council. Whereas approving in Imamiite jurisprudence, positive and international law, this entity could be a solution to many banking problems such as interest of commercial documents, documentary credits and purchase and sell of ordinary monetary debts