Every shipment carries a core set, plus product-specific documents that decide whether it clears. The core set is the commercial invoice, which customs values the goods against; the packing list, which states contents, weights and dimensions per package; the transport document, a bill of lading for sea freight or an air waybill for air; and the certificate of origin, which is what turns a trade agreement into an actual duty saving. On top of that, the product decides the rest: a phytosanitary certificate for plant products, a health or veterinary certificate for animal products, a fumigation certificate for many agricultural goods and wooden packaging, an EUDR due-diligence statement for the seven commodities that regulation covers when importing into the EU, and quality or analysis certificates where a grade is contractual. Two things cause most clearance delays. First, inconsistency between documents — the weight on the packing list disagreeing with the bill of lading, or the description differing from the invoice — because customs reads them against each other. Second, a certificate of origin issued for a tariff line the destination never liberalised, which is valid and worthless. Pre-clear documentation before arrival wherever possible: time-based charges such as demurrage and detention are the least predictable line in a landed-cost model and are almost always caused by paperwork rather than by shipping.