Primary forms (blooms, billets, slabs from initial casting) are distinguished from semifinished products by the stage of processing: primary forms emerge directly from solidification of molten metal, while semifinished products have typically undergone at least one rolling or reduction pass. The boundary can be fact-intensive, so mill process documentation and cross-referencing with HTS chapter notes is advisable.

Continuously cast strands that have not been rolled are generally treated as primary forms, but once they are cut to length and have defined cross-sectional dimensions consistent with semifinished product specifications, classification may shift. Consulting a licensed customs broker with the mill's process records is recommended when the distinction is unclear.