When ancillary components such as integrated controls, cold boxes, or heat exchangers are shipped as part of a complete functional unit, they may be classified with the principal machine under the composite goods rules. However, separately invoiced or separately shipped components are typically classified in their own headings, so importers should document the functional relationship clearly.

Beyond standard commercial invoices and packing lists, importers generally need detailed engineering specifications, country-of-origin certificates, and — for equipment containing pressure vessels — compliance documentation meeting applicable ASME or equivalent standards. If the machinery is subject to export controls in the country of origin, an export license copy may also be required.