This bill directs the Government Accountability Office (GAO), Congress's independent auditing agency, to investigate and report on how much money was spent on unused construction materials for the border wall project along the U.S.-Mexico border. The GAO must complete this study and submit its findings to Congress within 90 days of the bill becoming law. The legislation affects federal spending accountability and the Department of Homeland Security, which oversaw border wall construction. The bill does not authorize any new spending but rather requires an accounting of past expenditures to identify waste. By examining leftover materials, the study aims to provide Congress with concrete information about construction efficiency and cost management in the border wall project.