When a machine performs multiple functions, US Customs applies the 'essential character' or principal-function test. If cleaning and sorting is the dominant operation and milling is incidental, the heading for cleaning/sorting machinery is typically appropriate. If milling is the primary output, the machine may fall under a milling-machinery heading instead. A binding ruling request to CBP can provide certainty before importation.

For customs classification purposes, the distinction between seed-conditioning and grain-handling use does not change the heading — both applications fall here. However, seed-conditioning equipment sold for use with regulated seed varieties may be subject to USDA APHIS phytosanitary documentation requirements if it has been used with plant material prior to export.