Under the Trade Agreements Extension Act of 1951, the president is required to inform the US International Trade Commission (known until 1974 as the US Tariff Commission) of contemplated concessions in the tariff schedules. The commission then determines what the "peril point" is; that is, it informs the president how far the tariff may be lowered without injuring a domestic producer, or it indicates the amount of increase necessary to enable a domestic producer to avoid injury by foreign competition. Similarly, the act provides an "escape clause,"—in effect, a method for rescinding a tariff concession granted on a specific commodity if the effect of the concession, once granted, has caused or threatens to cause "serious injury" to a domestic producer. The Trade Expansion Act of 1962 grants the president the power to negotiate tariff reductions of up to 50% under the terms of GATT.
In 1974, The US Congress authorized the president to reduce tariffs still further, especially on goods from developing countries. As the cost of imported oil rose in the mid-1970s, however, Congress became increasingly concerned with reducing the trade imbalance by discouraging "dumping" of foreign goods on the US market. The International Trade Commission is required to impose a special duty on foreign goods offered for sale at what the commission determines is less than fair market value.
Most products are dutiable under most-favored nation (MFN) rates or general duty rates. The import tariff schedules contain over 10,000 classifications, most of which are subject to interpretation. Besides duties, the United States imposes a 17% "user fee" on all imports. Excise taxes and harsher maintenance fees are also imposed on certain imports. Under the terms of the North American Free Trade Agreement (NAFTA), which was approved by Congress in 1993, tariffs on goods qualifying as North American under the rules of origin will be phased out over a 15-year period.