For customs classification, a suit must comprise two or three garments (jacket plus trousers, and optionally a waistcoat) made of the same fabric, of the same color and composition, and presented together for retail sale. If the jacket and trousers are of different fabrics or colors, CBP will classify each piece separately under the applicable jacket or trouser heading, which can result in a different duty rate than the suit heading.

U.S. Customs requires that textile fiber content be declared on entry documentation and on the garment label in compliance with the Textile Fiber Products Identification Act. For wool suits, the declaration must specify the percentage of wool and any other fibers present. Discrepancies between declared and tested fiber content can result in redelivery demands, penalties, or reclassification, making pre-shipment lab testing advisable for high-value wool suit shipments.