The growing number of investment disputes indicates more challenging and controversial matters in the various arbitration practices. However, the International Centre for the Settlement of Investment Disputes (ICSID) rules do not entirely solve the problem in the arbitration process. This study aims to explain how the ICSID tribunal’s inherent reconsideration power can be exercised to “fill the gap” in arbitration proceedings. This study concludes that it can be enforced under Article 44 of the ICSID Convention, which decides the question submitted to the tribunal that the ICSID Convention does not cover. Second, in completing this study, the wording of Rules 19 of Arbitration Rules gives an almost similar order to the tribunals in the case of absence in the conduct of proceedings. Third, under Rule 38 (2) Arbitration Rules, the tribunals can exercise the reconsideration power when discovering new facts that decisively affect the case's outcome.