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What stacking means

A single import line can attract multiple duty layers at once. The LandedFees engine resolves each layer against its own statutory source and returns them as discrete rows in breakdown[]. Nothing is netted, folded, or hidden.

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The overlay families

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MFN (base rate)

The Most-Favored-Nation column-1 rate from the destination country’s tariff schedule. Sourced from USITC HTS (US), TARIC (EU), UK Trade Tariff (UK), and per-country schedules elsewhere. This is the floor.

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Section 232 (national security)

Applied per smelter country on steel and aluminum lines (HTS Chapters 72, 73, 74, 76). Russia-origin aluminum takes a 200 percent override regardless of exporting country. LandedFees reads the smelter_country field on each line and applies the correct layer even when the exporter is a passthrough.

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Section 301 (China-focused)

Ad valorem overlays on China-origin lines under HTS 9903.88.xx, from 25 percent (List 3, List 4A) down to 7.5 percent (List 4A reduced). Some tech goods carry active Section 301 exclusions; the engine resolves the current exclusion table and returns an exempted: true layer with a citation instead of the duty.

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Section 301-FL (fentanyl)

A separate Section 301 track under HTS 9903.03.02 layered on top of the base 301 rate. Applies to fentanyl-precursor chemistry lines. Returned as SEC_301_FL when in scope.

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Section 122 (balance-of-payments)

The 10 percent ad valorem overlay under HTS 9903.03.01, currently active. Applies to a broad slice of US imports across most origins. Returned as SEC_122. When the sunset provision is in effect the response ships a section_122 compliance flag.

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Section 338 (retaliatory)

Country-specific retaliatory duties under HTS 9903.90. Currently scoped to Canadian-origin goods in defined categories. Returned as SEC_338_CA.

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IEEPA overlays

Presidentially-invoked emergency tariff actions land under HTS Chapter 99 subheadings and are surfaced as their published code. The engine subscribes to the USITC Chapter 99 change stream so new IEEPA notices are picked up within one business day of publication.

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AD/CVD

Antidumping and countervailing duties are case-specific. Returned as AD_CVD with the case number in the layer note and a pga or ad_cvd compliance flag pointing at the ITC or Commerce final determination.

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FTA preferences

When usmca_qualifying: true or fta_id is set, the engine tries the preferential rate first. If the FTA rate beats MFN plus overlays, MFN is returned with exempted: true and an fta_qualified flag. When you did NOT claim an FTA but the origin qualifies, an fta_opportunity flag surfaces the potential savings.

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A stacked example

Wireless earbuds, HS 8517.62.00, origin CN, destination US, customs value $6,545. The engine returns:
MFN is 0 percent for this HTS line. Section 301 (List 4A, 25 percent) lands on the customs value. Section 122 (10 percent) lands on the same base. MPF and HMF are statutory customs fees, not duties, and show as separate layers. The engine computes each on its own base per statute so downstream systems can trace every dollar to a legal citation.

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Reading the flags

compliance_flags[] on the calc response carries any warnings the engine surfaced while resolving the layers. Common kinds:
  • section_122: Section 122 sunset scheduled; deadline reminder.
  • ad_cvd: active AD/CVD case matched; broker review recommended.
  • pga: Partner Government Agency review required (FDA, EPA, FCC).
  • fta_opportunity: a lower total exists under a claimable FTA.
  • data_gap: a layer could not be resolved; do not ship without broker review.
Each flag ships source, source_url, and legal_citation so your audit trail links directly to the underlying notice.