Rebalance for an Effective Defense Uniformed and Civilian Employees Act or the REDUCE Act This bill limits full-time positions in the Department of Defense (DOD), in each of FY2026-FY2030, to not more than 85% of the number of such positions at the end of FY2021. Not more than 1,000 of the positions may be career appointees within the Senior Executive Service. DOD may offer voluntary separation incentive payments and voluntary early retirement payments to achieve the reductions but must use involuntary measures, beginning at the start of FY2021, to achieve required reductions in personnel levels if voluntary measures are inadequate.