Classification identifies the HTSUS provision; the rate columns attached to that provision determine what is owed. The General column of Column 1 carries the normal trade relations (most-favored-nation) rate that applies to most countries, the Special column lists preferential rates under trade agreements and programs, and Column 2 applies higher statutory rates to the few countries without normal trade relations. A rate may be ad valorem (a percentage of value), specific (an amount per unit), or compound (both).
Duty is rarely the whole bill. Most formal entries also owe the Merchandise Processing Fee, an ad valorem user fee with a minimum and a maximum per entry, and many goods are subject to additional Chapter 99 duties under Section 301, Section 232, or IEEPA that stack on top of the base rate. Because each of these follows from the classification and the country of origin, a classification error usually surfaces first as a duty error. The entries in this category explain each rate type and how it is applied.