Slips are undergarments worn beneath outer clothing, while nightdresses are sleepwear. CBP considers design, marketing, labeling, and construction when the distinction is unclear. A garment marketed and labeled as sleepwear will generally be classified as a nightdress even if it resembles a slip in construction.

Yes. All textile apparel imported into the US must comply with the Textile Fiber Products Identification Act, requiring fiber content labels, country of origin marking, and manufacturer or importer identification. The FTC enforces these labeling rules, and non-compliant shipments can be detained at the port of entry.