Reducing Costs of DHS Acquisitions Act This bill requires notification of the Management Directorate of the Department of Homeland Security (DHS) and Congress if a major acquisition program of DHS fails to satisfy any approved cost, schedule, or performance threshold. Major acquisition program means (1) a capital asset, service, or hybrid acquisition program that is estimated by DHS to require an eventual total expenditure of at least $300 million over the life-cycle cost of the program; or (2) an acquisition program identified as a program of special interest. If such a failure occurs, or is expected to occur, the bill requires a remediation plan and root cause analysis. The Management Directorate must review such plan and either approve it for continuation or provide an alternative proposed corrective action.