Auditing Islamic, financial institutions by Shari'a is a relatively new industry; thus, there is an urgent need for established rules and theories in order to make it a more stable field. This research shows the extent to which the auditing industry needs to prepare an internal auditing procedure manual.

In the first section of this study, the researcher defines the term "internal auditing procedure." Then, he briefly discusses the legality of auditing and its divisions. In the second section, the researcher draws the parameters of the internal auditing procedure manual; then he mentions the most important procedures that the auditor must perform prior to, during, and after its implementation.

In the third section, he shows how the internal auditing procedure manual can be applied to investment funds as one of the Islamic, financial institutions' activities. Finally, he attaches a proposed form regarding the application of internal auditing to investment funds