U.S. imports of Heterocyclic Compounds with Nitrogen Hetero-Atoms Only (NES) (SITC 51577) totaled $89.9M in August 2026, imported from 40 countries.
Importers of Heterocyclic Compounds with Nitrogen Hetero-Atoms Only (NES) paid $5.9M in duties in August 2026, an average duty rate of 6.77% — duty actually collected as a share of the imports that cleared customs, not the published tariff schedule. Heterocyclic Compounds with Nitrogen Hetero-Atoms Only (NES) imports of $89.9M in August 2026 ran 34% below the year-to-date monthly average of $136.6M.
Last updated: August 2026 dataNitrogen-only heterocyclic compounds not elsewhere specified represent the residual catch-all for ring systems — such as azepines, diazines not covered by pyrimidine headings, and multi-nitrogen scaffolds — that do not fit any of the more specifically enumerated nitrogen-heterocycle subheadings. Because this is a residual category, classification here requires a process of elimination: the compound must be confirmed as not classifiable under pyrazole, imidazole, pyridine, quinoline, pyrimidine, piperazine, triazine, or phenothiazine headings. Many novel pharmaceutical scaffolds and agrochemical candidates land here during early-stage API development.
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976 import shipments a month
The classifier should work through each named nitrogen-heterocycle subheading in order — pyrazole, hydantoin, imidazole, pyridine, quinoline, pyrimidine/piperazine/triazine, and phenothiazine — and confirm the compound's ring system does not match any of them. Only after ruling out all named categories should the compound be placed in the NES subheading. A licensed customs broker with fine-chemical expertise is advisable for novel or complex structures.
Many nitrogen heterocyclic intermediates sourced from China fall within HTS chapters subject to Section 301 tariffs, and the NES category is no exception. Because this is a residual grouping covering diverse structures, the applicable 10-digit HTS code — and its Section 301 status — must be verified for each specific compound before importation.
Basic heading 40 of 465 in section 5
Basic heading 51577 · $89.9M of $27.5B
Imports · August 2026
origin
China and Ireland together supply 51% of it.
customs district
Census does not publish district detail for this classification system.
destination
Census does not publish state detail for this classification system.
entry
Census does not publish port detail for this classification system.
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ImportsExports
Imports
$89.9MYoY · free account
Exports
$17.8MYoY · free account
12-mo low · imports
Low · free accountOver the twelve months to August 2026, the U.S. imported $1.5B of Heterocyclic Compounds with Nitrogen Hetero-Atoms Only (NES) and exported $404.5M.
Through August 2026. Source: U.S. Census Bureau.