The Department of Defense (DOD) relies extensively on contractors to equip and support the U.S. military in peacetime and during military operations. Contractors design, develop, and build advanced weapon and business systems, construct military bases around the world, and provide services such as intelligence analysis, logistics, and base support. Congress has long been frustrated with perceived cost overruns, waste, mismanagement, and fraud in defense acquisitions, and has spent significant effort attempting to reform and improve the process. Since the 1970s, there have been numerous efforts to comprehensively reform defense acquisition. Congress generally sets acquisition policy for the DOD through the annual National Defense Authorization Acts (NDAAs) as well as through stand-alone legislation, such as the Defense Acquisition Workforce Improvement Act of 1990, Federal Acquisition Streamlining Act of 1994, Clinger-Cohen Act of 1996, and Weapon System Acquisition Reform Act of 2009. This report provides a brief overview of selected acquisition-related provisions found in the NDAAs for FY2016 ( P.L. 114-92 ), FY2017 ( P.L. 114-328 ), and FY2018 ( P.L. 115-91 ). This report also has a section on some of the more controversial and extensive changes in recent years: the changes to the role of the Chiefs of the Military Services and the Commandant of the Marine Corps (collectively referred to as the Service Chiefs) in the acquisition process, the breakup of the office of the Under Secretary of Defense for Acquisition, Technology, and Logistics (USD [AT&L]), and the shift of authority from the Office of the Secretary of Defense (OSD) to the military departments. In recent years, Congress has generally exercised its legislative powers to affect defense acquisitions through Title VIII of the NDAA, entitled Acquisition Policy, Acquisition Management, and Related Matters . In some years, the NDAA also contains titles specifically dedicated to aspects of acquisition, such as Title XVII of the FY2018 NDAA, entitled Small Business Procurement and Industrial Base Matters . Congress has been particularly active in legislating acquisition reform over the last three years. For FY2016-FY2018, NDAA titles specifically related to acquisition reform contained an average of 82 provisions (247 in total), compared to an average of 47 such provisions (466 in total) in the NDAAs for the preceding 10 fiscal years (see Appendix A and Appendix B ). The FY2016 NDAA sought to develop more timely and efficient ways for DOD and the Military Services to acquire goods and services. One provision expanded the use of rapid acquisition authority to support certain military operations. Another provision required DOD to develop guidance for rapidly acquiring middle tier programs (intended to be completed in two to five years), to include rapid prototyping and rapid fielding. Congress also required the development of streamlined alternative acquisition paths that maximize the use of flexibility allowed under the law to acquire critical national security capabilities. In addition to expanding existing flexibilities and trying to create new and quicker acquisition methods, Congress authorized the Secretary of Defense to, in certain circumstances, waive any provision of acquisition law or regulation if (1) the acquisition of the capability is in the vital national security interest of the United States; (2) the application of the law or regulation to be waived would impede the acquisition of the capability in a manner that would undermine the national security of the United States; and (3) the underlying purpose of the law or regulation to be waived can be addressed in a different manner or at a different time. In the FY2017 NDAA, Congress reflected its concern with defense technology innovation, dedicating a number of sections to promoting integration and collaboration of the national technology and industrial base, and attempting to spur defense-related innovation among nontraditional defense and small businesses. Other transaction authority (OTA) allows DOD, using the authority found in 10 U.S.C. 2371, to enter into transactions with private organizations for basic, applied, and advanced research projects. OTA, in practice, is often defined in the negative: it is not a contract, grant, or cooperative agreement, and its advantages come mostly from exempting OTA transactions from certain procurement statutes and acquisition regulations. The FY2016 NDAA expanded DOD's ability to use Other Transaction Authority for certain prototype programs, including making some authorities permanent. Subtitle G of Title VIII of the FY2018 NDAA— Provisions Relating to Other Transaction Authority and Prototyping —contains eight sections aimed at expanding and improving the use of OTA. The FY2016 NDAA required numerous reports and chartered efforts to explore ways to improve defense acquisition. The most comprehensive such effort was the establishment of the Advisory Panel on Streamlining and Codifying Acquisition Regulations (knows as the 809 Panel after the section of the NDAA establishing the group). The 809 Panel was tasked with finding ways to streamline and improve the defense acquisition process. The independent panel has two years to develop recommendations for changes in the regulation and associated statute to achieve those ends, and must report the recommendations to the Secretary of Defense and to Congress. The FY2016 NDAA also required each Service Chief to submit a report on linking and streamlining the requirements, budget, and acquisition processes; and the Secretary of Defense and Joint Chiefs of Staff to review the requirement, budgeting, and acquisition processes, in part to determine the "advisability of providing a time-based or phased distinction between capabilities needed to be deployed urgently, within 2 years, within 5 years, and longer than 5 years." The FY2018 NDAA established a three-year pilot program requiring certain companies filing a Government Accountability Office (GAO) bid protest to pay DOD processing costs for the protest when GAO issues an opinion that denies all elements of the protest. The pilot program would begin two years from enactment of the bill. A m icro - purchase is an acquisition of supplies or services using simplified acquisition procedures, the total amount of which does not exceed the micro-purchase threshold. The FY2017 NDAA raised DOD's micro-purchase threshold from $3,500 to $5,000. The FY2018 NDAA raised the micro-purchase threshold for the rest of the federal government to $10,000, thus establishing a different threshold for DOD vis-à-vis other federal agencies. A s implified acquisition is a streamlined method for making purchases of supplies or services. The simplified acquisition threshold delineates what types of purchases can use this streamlined method. The FY2018 NDAA also increased the simplified acquisition threshold from $100,000 to $250,000. The FY2017 NDAA clarified Congress's desire to see DOD increase its use of 1. fixed price contracting, (requiring a regulation establishing a preference for such contracts, and generally requiring fixed-price contracts for foreign military sales); and 2. performance-based contract payments. The FY2017 NDAA also restricted the use of l o west price technically a cceptable (LPTA) source selection criteria to certain circumstances, and specifically calls for avoiding using LPTA for IT and related services, personal protective equipment, and knowledge-based services. LPTA is a source selection process where the government determines that the lowest price is the determining factor for award as long as the bidder meets the technical requirements of the solicitation. LPTA is appropriate only when the government "expects" it can achieve best value from selecting the proposal that is technically acceptable and offers the lowest evaluated price. The FY2018 NDAA required DOD to adhere to commercial standards for risk and materiality when auditing costs incurred under flexibly priced contracts and requires the use of qualified private auditors to ensure the auditing needs of DOD are met, and raising the threshold (as well as making other modifications) to required submissions of certified cost and pricing data. The FY2017 NDAA required major defense acquisition programs (MDAPs) to be designed and developed using "a modular open system architecture approach to enable incremental development and enhance competition, innovation, and interoperability." The open architecture requirements extend to major system interfaces and standards for use in major system platforms. The act also generally establishes the authority to conduct and establish funding for prototype projects when there is a high-priority warfighter need due to a capability gap, there is an opportunity to integrate new components into a major weapon system based on commercial technology, the technology is expected to be mature enough to prototype within three years, and there is an opportunity to reduce sustainment costs. In an effort to gain visibility into MDAPs and rein in cost growth, the FY2017 NDAA requires the Secretary of Defense to assign program cost and fielding targets to MDAPs before funds are obligated for development. It also requires that after each milestone decision, the milestone decision authority provide Congress with an "acquisition scorecard" that includes estimated cost, schedule, and technology risk information. Reflecting congressional concern with the sustainment and total life-cycle costs of MDAPs, the FY2017 NDAA required a number of DOD actions, including initiating a review by an independent entity to determine the extent to which sustainment is considered in acquisition decisions, and conducting sustainment reviews of programs five years after initial operational capability. The act also repealed chapter 144a of Title 10, which created a separate category of acquisition for major automated information systems (§846). The FY2018 NDAA also contained a number of provisions relating to MDAPs, including a provision excluding defense business systems and major automated information systems from the definition of an MDAP; and one prohibiting the use of an LPTA source selection process for development contracts. Other sections would add new requirements aimed at emphasizing reliability and maintainability in MDAPs, and focus on test and evaluation plans and data analysis.