Additional U.S. Rules of Interpretation
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The Additional U.S. Rules of Interpretation are four HTSUS rules that supplement the GRIs: Rule 1(a) governs principal-use provisions; 1(b) actual-use provisions; 1(c) provisions for parts or accessories; and 1(d) provisions describing textile materials. They apply to U.S. tariff classification unless the context otherwise requires.
In Detail
Rule 1(a) — Principal use: When a heading or subheading uses a use-based phrase such as "of a kind used for," "designed for use with," or "principally used in," Rule 1(a) directs classification by the principal use in the United States of the class or kind of goods to which the imported goods belong. The analysis is not based on a specific importer's intended use but on the general commercial principal use of that product class, identified using factors such as physical characteristics, channels of trade, and purchaser expectations.
Rule 1(b) — Actual use: For a provision that requires a specified actual use, the goods must in fact be put to that use, and — unless the provision states otherwise — the use must occur within three years after the date of entry, with proof of that use furnished to CBP within that period. Actual use is a narrower, fact-specific classification rule distinct from principal use, which looks at the class or kind of goods rather than the individual shipment's post-importation use.
Rule 1(c) — Parts and accessories: A provision for parts or accessories applies to an article identifiable as a part or accessory designed for use with a particular article, but only if a more specific provision does not separately describe that part or accessory as an article in its own right. This specificity limitation means a parts-and-accessories provision is generally residual to any heading that names the component directly.
Rule 1(d) — Textile materials: A textile category good that is a blend or combination of two or more textile materials is classified as if it consisted wholly of the single textile material that predominates by weight, unless the heading text, a legal note, or another provision specifies a different rule for that particular mixture.
Classification Significance
The Additional U.S. Rules matter most in HTSUS chapters where headings are defined by use — agricultural equipment, sporting goods, medical devices, professional tools, and certain textile and chemical categories. Classifiers working in these chapters must apply Rule 1(a) to determine principal use rather than relying on product description alone. Failure to apply these rules in use-provision headings is a documented source of classification error that generates audit exposure.
How Kanon Handles This
Kanon captures intended use and product class as attributes during intake and evaluates them against applicable use provisions in the HTSUS. Where a heading requires principal use analysis under Rule 1(a), Kanon documents the provision, the product class, and the basis for the principal use determination in the Classification Support Package.