Antidumping and Countervailing Duties: Information on Actions by Commerce and CBP to Address Reported Weaknesses in Duty Collection Processes, Briefing for Senate and House Appropriations Homeland Security Subcommittees [open pdf - 1MB]
From the Document: "The United States assesses antidumping (AD) duties on products imported at unfairly low prices and countervailing (CV) duties on products subsidized by foreign governments to address injury to domestic industries. The U.S. system for determining AD/CV duties involves the setting of an initial estimated duty rate upon the entry of goods into U.S. commerce, followed by the retrospective assessment of a final duty rate. The Department of Commerce (Commerce) sets an initial estimated AD/CV duty rate, based on a calculation of the estimated margin of dumping or the estimated amount of subsidy, and later determines a final duty rate based on the actual amount of dumping or subsidization that occurred. U.S. Customs and Border Protection (CBP) is responsible for collecting the estimated duties owed at the time of entry, which are based on the initial rate. [...] In 2016, we reported that CBP continued to face challenges collecting payment on supplemental AD/CV duty bills, attributable in part to the U.S. government's retrospective assessment of final duties owed and the complex and lengthy process for determining final AD/CV duty rates. According to Commerce, the United States is the only major user of AD/CV duty trade remedies that implements a retrospective system of duty assessment."
Government Accountability Office: http://www.gao.gov/