The NES designation is a residual category, and CBP may question whether a product genuinely lacks a more specific classification or is being placed here to avoid a higher duty rate or regulatory requirement. Importers should document why no more specific heading applies, supported by technical data sheets and Safety Data Sheets, and be prepared to provide laboratory analysis if requested.

All chemical substances imported into the US must comply with TSCA unless specifically exempt. Importers must certify at entry that each chemical substance in the preparation is either on the TSCA Chemical Substance Inventory or subject to an applicable exemption or notification. Given the heterogeneous nature of NES preparations, a substance-by-substance review of the formulation against the TSCA inventory is strongly recommended before shipment.