Miss. Code § 77-7-293
After an order or decision has been made by the commission, any party to the proceedings may, within thirty (30) days after the entry of the order or decision, apply for a rehearing in respect of any matters determined in such proceedings and specified in the application for rehearing, and the commission may grant and hold such rehearings on such matters.
The commission shall either grant or refuse an application for rehearing within twenty (20) days after the date of application therefor. A failure by the commission to act upon such application within that period shall be deemed refusal thereof. If the application is granted, the commission shall conduct and conclude a rehearing within thirty (30) days of the entry of the order for rehearing and shall enter a new order after the rehearing shall have been concluded. Such new order shall become effective ten (10) days after it is entered, unless otherwise provided by the commission for reasonable cause.
Miss. Code § 77-7-293