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October 2025, question 31

Classification · Classification: GRIs, notes and headings

Of the four choices below, which is the best CLASSIFICATION of diammonium hydrogenorthophosphate?

  1. Heading 2805
  2. Heading 3104
  3. Heading 3102
  4. Heading 3105
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CBP's answer: D. D: Heading 3105

Chapter 31 Note 5 says diammonium hydrogenorthophosphate (diammonium phosphate) is classified in heading 3105, and 3105.30 is that substance. Heading 2805 is for metals, 3102 for nitrogen fertilizers and 3104 for potassic fertilizers.

diammonium hydrogenorthophosphate (diammonium phosphate), whether or not pure, and intermediates thereof, are to be classified in heading 3105 Chapter 31, Note 5

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CBP's key cites: Chapter 31, Note 5; HTSUS 3105.30.0000

Question and key from CBP's October 2025 exam and answer key. The walk-through is ours; quotes are from the pinned editions in the reference viewer (HTSUS 2026 Basic, 19 CFR 2025 edition).