Ad Valorem Duty
An ad valorem duty is a tariff expressed as a percentage of the customs value of the imported goods — for example, "5% ad valorem." It is the most common duty structure in the HTSUS and is calculated by multiplying the duty rate by the customs value, which for most imports is the transaction value: the price actually paid or payable for the goods.
In Detail
Ad valorem (Latin: "according to value") duties scale with value: a higher-value import of the same product pays more duty than a lower-value import. The customs value used in the calculation is determined under the Customs Valuation Agreement (part of the WTO framework) implemented in U.S. law under 19 USC §1401a. Transaction value — the invoice price adjusted for certain additions (assists, royalties, packing costs paid by the buyer) and deductions (international freight if separately stated) — is the preferred valuation method, applied when a sale exists and the buyer and seller are not related in a way that affects the price.
Ad valorem duties contrast with two other duty structures present in the HTSUS. Specific duties are assessed per unit of quantity — "$0.50 per kilogram," for example — without reference to value. Compound duties combine both: "5% ad valorem plus $0.25 per kilogram." Ad valorem is by far the most common form, but specific and compound duties appear in agricultural products, certain chemicals, footwear, textiles, and other categories where Congress chose a quantity-based rather than value-based assessment.
Because ad valorem duties scale with customs value, customs valuation is as important as HTS classification to the total duty calculation. Importers who undervalue goods — whether through incorrect transaction value determination, failure to include dutiable assists, or related-party pricing at non-arm's-length values — underpay ad valorem duties. CBP's customs valuation enforcement is coordinated with classification enforcement and routinely examined in Focused Assessments alongside HTS code review.
Classification Significance
The HTS code determines the duty type. When the applicable rate is ad valorem, the total duty is a joint function of the correct HTS code (the rate) and the correct customs value (the base). A correct HTS code paired with an incorrect customs value produces an incorrect duty calculation with the same compliance exposure as a wrong HTS code. Both inputs to the ad valorem formula must be accurate, and both are examined in a CBP audit.
How Kanon Handles This
Kanon's Classification Support Package identifies the duty type — ad valorem, specific, or compound — applicable to the classified HTS code, along with the applicable rate. Where the duty is ad valorem, the package documents the rate so the importer can apply it against the correct customs value to produce an accurate duty calculation.