In all legal systems, it’s essential to know the nature of fault due to the absolute responsibility of a salesman or producer, on the one hand, and the possibility of receiving compensation on the other hand. In Islamic law, this absolute responsibility is interpreted as ḍamān (indemnification); therefore, this ḍamān that is our subject of discussion in option of defect, is taken into consideration when preparing legal statements as well as in transactions. Thus by realizing the issue, that is, the defect and by expressing its properties and solving possible conflicts, it is made easy to enforce the propositions related to defect. This paper tries to review some criteria of defect, as well as pondering on its nature, and by presenting ideal criteria, facilitates annulment or correction of a deal and enforcing the propositions of option and receiving compensation or refund.