Indigo and certain other vat dyes can function either as fiber-reactive vat dyes or as insoluble pigments in printing inks and coatings. The heading explicitly captures both uses, so the same chemical substance is correctly classified here regardless of whether the end use is textile dyeing or pigment application — provided it meets the chemical definition of a vat dye.

A commercial invoice, packing list, and bill of lading are standard. Because synthetic indigo is a chemical substance, importers should also confirm TSCA compliance. If the product is imported in bulk liquid form, a Safety Data Sheet (SDS) and proper hazardous materials labeling under DOT regulations may be required. Country-of-origin documentation is particularly important given Section 301 exposure for Chinese-origin chemical products.