Okla. Stat. tit. 74, § 291.1

Members of the Legislature shall be allowed a per diem in lieu of expenses in an amount authorized by the provisions of the Internal Revenue Code of 1986, as amended, for deductibility of expenses for travel while away from home without additional documentation for each night spent away from home in the performance of their official duties within the state during regular and extraordinary legislative sessions, not to exceed the number of legislative days per week.