Okla. Stat. tit. 19, § 1418

A county budget board may authorize transfers of any unencumbered and unexpended appropriation or any portion thereof from one expenditure category to another within the same department or from one department to another within the same fund, except that no appropriation for debt service or other appropriation required by law or resolution may be reduced below the minimums required. Interfund transfers may be made only as authorized by this act or as provided in the budget as adopted or amended according to Sections 10, 14 and 20 of this act.