Certified seed corn for sowing falls under 100510 and must meet USDA APHIS import permit and phytosanitary certificate requirements. All other corn — including feed, food-grade, and industrial-use grain — falls under 100590 and may be subject to tariff-rate quota treatment. The distinction turns on whether the corn is certified for planting, not simply on variety.

Corn containing genetically engineered events not approved by USDA and FDA for US use can be refused entry. Importers should verify that the biotech event profile of the shipment matches the US approval registry before the cargo departs, particularly for grain sourced from countries with different approval landscapes.