How to calculate US import duties

TL;DR

• US import duty is computed line by line on the entry summary, not per shipment. Each HTS line gets its own stack of an MFN base rate plus any Chapter 99 secondary rates that apply.
• Five inputs drive every line: 10-digit HTS code, country of origin, country of melt-and-pour or smelt-and-cast for metals, declared customs value, and entry date.
• The layers that stack as of May 2026: MFN base, Section 232 metals (50% steel and aluminum, 200% on Russia-aluminum), Section 301 China, Section 122 surcharge (the IEEPA replacement, 10% through July 24, 2026), AD/CVD where the order's scope language reaches the product, and any preference-program offset (USMCA, KORUS, AGOA, CBI, and the rest). MPF and HMF are user fees that apply on top.
• The Tandom calculator at tariffs.tandom.ai/calculator does the full stack, returns the codes in ACE reporting order, and cites the regulatory authority behind every line.

The landed-duty formula

The math is straightforward additive arithmetic at the line level:

Total duty (per line) =
    Customs value × (MFN rate + Σ Chapter 99 rates)
  + AD/CVD assessed amount
  + MPF (entry-summary level, capped)
  + HMF (entry-summary level, ocean only)

The customs value comes from 19 USC 1401a, the transaction-value rule. It is the price actually paid or payable when the goods are sold for export to the US, plus required additions (assists, royalties tied to the sale, tooling, packing, selling commissions paid by the buyer, proceeds returning to the seller). International freight, insurance, and US duties are excluded when separately stated on the invoice.

Per line, not per shipment

An entry summary with twelve different HTS classifications has twelve separate duty calculations. MPF is computed once at the entry-summary level (not per line) and is capped per fiscal year. HMF is computed once at the entry level for ocean shipments, with no cap.

Most layers are ad valorem

A 25% MFN rate, a 25% Section 232 add-on, and a 25% Section 301 add-on sitting on the same line all multiply the same dutiable value, then sum together to a 75% effective rate. Some HTS items still carry specific (per kilogram, per liter, per piece) or compound rates, mostly in agriculture, textiles, and footwear. Section 232, Section 301, Section 122, and IEEPA-era proclamations are always ad valorem.

AD/CVD is on top, never offset

AD/CVD is a cash deposit at entry. Final liquidation rates are set 12 to 18+ months later through Commerce's administrative review. The deposit is not refunded by a preference program or a Chapter 99 exclusion. It is its own track.

Step by step

For any line on the entry summary, work the same six steps.

1. Classify to the correct 10-digit HTS code

The first six digits are the international Harmonized System; digits 7 through 10 are US-specific statistical breakouts. Authoritative source is hts.usitc.gov. If you are between two codes, work the classification ladder (rule of relative specificity, essential character, General Rules of Interpretation in order); for sets and composite articles see mixed-materials classification. The Tandom HTS Catalog at tariffs.tandom.ai/hts-catalog is an instrumented copy of the same data with duty information attached.

2. Confirm country of origin

Origin is where substantial transformation last occurred, not where the goods last shipped from. Per 19 CFR 134.1, the test is name, character, and use. A Chinese factory's product trans-shipped through Vietnam is still China-origin and carries China-origin tariffs. Origin under preference programs (USMCA, KORUS, etc.) is determined by tariff-shift or regional-value-content rules from the agreement text, which is a stricter test than substantial transformation.

3. Identify country of melt-and-pour (steel) or smelt-and-cast (aluminum)

For Section 232 derivatives in HTS Chapters 73, 76, 82, 83, 84, 85, and 87, this is a separate field from origin. The country where the metal was first solidified (steel) or last cast (aluminum) determines whether the 50% Section 232 rate applies, the 25% UK rate applies under the May 2025 US-UK deal, or the 200% Russia-aluminum rate applies. Aluminum entered with smelt-and-cast country "unknown" pays the 200% rate by default since June 28, 2025.

4. Establish the entry date

Per 19 CFR 141.69, the rate of duty is the rate in effect at the time of entry as defined in 141.68. Not the date of export, not the date of arrival. A few specific Executive Orders carve out goods on the water before a proclamation date, but those carve-outs are written into the proclamation itself.

5. Set the customs value

Default is transaction value per 19 USC 1401a. Add assists, tooling, royalties tied to the sale, packing costs incurred by the buyer, and selling commissions paid by the buyer. Subtract international freight, insurance, and US duties when separately stated. If transaction value is unavailable (related-party sales failing the circumstance-of-sale test, conditional sales, etc.), the fallback hierarchy is: identical-merchandise transaction value, similar-merchandise transaction value, deductive value, computed value, and finally a "reasonable" method. Importers can request computed value before deductive value.

6. Pull every applicable tariff layer

Run the 10-digit code, origin, and entry date through each authority: Section 232 metals, Section 301 lists and exclusions, Section 122 surcharge, AD/CVD orders by HTS heading and country, and any preference program for which the goods qualify. Each layer either adds an ad valorem percentage to the MFN base, replaces the MFN base with a preferential rate, or assesses a separate amount (AD/CVD, MPF, HMF).

What's in each layer

The landed-duty rate is the sum of every applicable tariff layer for the entry's HTS code, country of origin, and entry date. Each layer below sits in a specific ACE reporting position and has its own legal authority.

MFN (Column 1 General)

The default rate for any World Trade Organization member origin. Found in the "General" sub-column of Column 1 in the HTSUS. Rates run from 0% (free) to 30%+ (textiles, footwear, some agricultural items). The "Special" sub-column lists preference-program rates, indexed by SPI letter (S for USMCA, KR for KORUS, A for GSP, D for AGOA, etc.).

Column 2 is a separate column reserved for non-WTO origins. As of 2026, only four countries are Column 2: Cuba, North Korea, Belarus, and Russia. Belarus and Russia were moved by the Suspending Normal Trade Relations with Russia and Belarus Act (Pub. L. 117-110, signed April 8, 2022). Column 2 rates are typically 30 to 80% on items where Column 1 is single digits.

Section 232 (steel, aluminum, copper)

Tariffs under Section 232 of the Trade Expansion Act of 1962. The current regime took shape with Proclamations 10895 (aluminum) and 10896 (steel) in February 2025, which terminated all prior country exemptions and quota deals as of March 12, 2025. The rate was doubled from 25% to 50% on June 4, 2025 for both steel and aluminum and their derivatives.

Country-specific rates that sit on top:

• UK: 25% (vs. 50%) under the May 8, 2025 US-UK Economic Prosperity Deal.
• Brazil: 10% on a defined subset of products.
• Russia (aluminum): 200% under Proclamation 10522 (March 2023), codified at 9903.85.67 and 9903.85.68. Aluminum derivatives entered with smelt-and-cast "unknown" carry the same 200% rate by default since June 28, 2025.

Derivative-products lists. Section 232 reaches well beyond Chapters 72, 73, and 76 where steel and aluminum live in raw form. The 2025 derivative annexes brought items in HTS Chapters 73, 76, 82, 83, 84, 85, and 87 (notably 8708.10.30 and 8708.29.21 on steel content). For derivatives outside Chapters 72/73/76, the duty applies only to the steel or aluminum content value, not the entered value of the whole article. CBP's preferred reporting is two lines: a non-metal Line 1 carrying the original HTS at full value with no Chapter 99 code, and a metal-content Line 2 carrying the same HTS at quantity zero plus the 9903 code, with the duty calculated against the metal content value.

ACE reporting. Effective April 6, 2026, the 232 metals families consolidated to the 9903.82 family for steel, aluminum, and copper. Pre-April-6 entries used 9903.80 / 9903.81 (steel), 9903.85 (aluminum), and 9903.78 (copper). The Russia-aluminum codes 9903.85.67 and .68 carry forward.

Section 301 (China)

Tariffs under Section 301 of the Trade Act of 1974, on goods of China origin. The four-list architecture is still in force:

• List 1: 25%
• List 2: 25%
• List 3: 25%
• List 4A: 7.5%
• List 4B: suspended since the December 2019 Phase One announcement

The USTR completed its statutory four-year review on September 13, 2024. The increases on strategic-sector goods took effect September 27, 2024 and rolled in through 2025 and 2026:

• Electric vehicles: 100%
• Lithium-ion EV batteries: 25% (non-EV batteries staged to 25% in 2026)
• Semiconductors: 50% effective January 1, 2025
• Solar cells: 50%
• Ship-to-shore cranes: 25%
• Certain steel and aluminum products: 25%
• Syringes and PPE: 25 to 50% staged

Chapter 99 reporting. 9903.88.01 through 9903.88.04 cover the original lists; 9903.88.15 covers List 4A; the four-year-review categories use new 9903.88.6x and 9903.91.x codes per the September 2024 USTR FRN.

Active product-specific exclusions: 178 as of late 2025 (164 product-specific plus 14 solar-manufacturing equipment), most expiring November 10, 2026. Exclusions are time-bounded; the certificate must bracket the entry date. Some exclusions require the importer to be a specific named party.

Hong Kong (ISO HK) is exempt from Section 301 even though CBP requires "Made in China" physical marking under EO 13936. Report HK as country of origin. Treating HK as China for tariff purposes is a recurring filing mistake.

Section 122 (the IEEPA replacement)

A 10% temporary import surcharge under Section 122 of the Trade Act of 1974, effective 12:01 a.m. ET February 24, 2026. Section 122 is uniform across countries, capped at 15% ad valorem, and cannot exceed 150 days without an Act of Congress, so it terminates July 24, 2026 absent legislative extension.

It does not stack on Section 232. If 232 applies to a line, Section 122 does not. It does stack on Section 301, AD/CVD, and the MFN base.

Section 122 replaced the IEEPA reciprocal-tariff regime that the Supreme Court struck down in Learning Resources, Inc. v. Trump (decided February 20, 2026, 6-3). The Court held that the International Emergency Economic Powers Act does not authorize tariffs. CBP stopped collecting IEEPA duties at 12:01 a.m. ET February 24, 2026. Refund mechanics for the roughly $130 to $175 billion already collected remain unresolved as of May 2026. For pre-February-24, 2026 entries, the IEEPA codes (9903.01.x, 9903.02.x, 9903.96.01-.02) are part of the historical record but no longer applicable on new entries.

AD/CVD (antidumping and countervailing)

Cash deposits at entry under Title VII of the Tariff Act of 1930. Commerce sets cash-deposit rates in preliminary, final, and administrative-review determinations published in the Federal Register. The deposit at entry is provisional. Final liquidation rates are set 12 to 18+ months later through Commerce's administrative review.

Determining the right rate. Identify both the manufacturer and the exporter (these can be different entities). If the exporter has a company-specific rate, use that. Otherwise the manufacturer-specific rate. Otherwise the all-others rate (market-economy cases) or the country-wide rate (non-market-economy cases like China, Vietnam). Some orders assign rates by exporter/manufacturer combination, not by either alone.

Scope. The scope text in the original FR order, plus any Commerce scope determination, defines what is covered. Scope is described in product terms; the HTS codes listed in the order are advisory, not dispositive. A product can be inside scope even if its HTS code is not listed, and outside scope even if it is. Wrong scope assessment is a major bite (200%+ unexpected deposits), with refund only after a successful scope ruling.

Where to find them. The Tandom AD/CVD catalog mirrors Commerce ITA's active case list and is the working source for daily broker lookups. The Investigations view shows pending USITC cases. CBP CSMS messages issue specific liquidation instructions per case (see the CSMS triage guide). The Tandom catalog indexes about 736 unique active cases (951 order records when AD and CVD count separately) and searches by HTS code, country, manufacturer, and entry date.

Commerce's January 15, 2025 final rule (89 FR 57286) revised cash-deposit collection methods, NME-rate methodology, all-others-rate calculation, and respondent-selection rules. Brokers handling AD/CVD entries since January 2025 should re-verify their procedures.

PGA flagging (not duties, but they gate entry)

Partner Government Agency requirements gate the entry. They are not duties, but they will hold or refuse the goods. The high-frequency agencies:

• FDA (food, drugs, devices, cosmetics, radiation-emitting electronics): prior notice for food, facility registration, FDA product code, sometimes affirmation of compliance.
• USDA APHIS (plants, animals, wood-packaging ISPM-15, agriculture): permits, phytosanitary certificates.
• USDA FSIS (meat, poultry, egg products): inspection.
• EPA (engines and vehicles, FIFRA pesticides, TSCA chemicals, refrigerants): EPA Form 3520-1, TSCA certification.
• CPSC (consumer products): Certificates of Compliance for children's products today; eFiled CoCs in ACE PGA Message Set required for all CPSA-regulated finished products effective July 8, 2026 (or January 8, 2027 from FTZs).
• ATF (firearms, ammunition, explosives): Form 6.
• APHIS Lacey Act (plants and plant products): declaration.
• FCC (radio-frequency devices): SDoC/740 process.
• DOT NHTSA (motor vehicles): HS-7 declaration.

A duty calc that says zero AD/CVD is still meaningless if EPA holds the entry on a TSCA certification gap. PGA flags travel with the same HTS code and country combination that drives the tariff stack.

SPI claims (preference programs)

Special Programs Indicator codes flag preference-program eligibility. The active programs:

• USMCA: SPI "S" for general claims, "S+" for certain agricultural goods and TPL apparel. The first joint USMCA review is July 2026.
• KORUS (US-Korea): SPI "KR".
• JPEPA (US-Japan): SPI "JP".
• AGOA: SPI "D" or "D+" (textile/apparel). AGOA is statutorily separate from GSP, so it remains active even when GSP is expired.
• CBI / CBTPA (Caribbean Basin): SPI "E" and "R".
• Israel FTA: SPI "IL".
• Singapore, Australia, Bahrain, Chile, Colombia, Morocco, Oman, Panama, Peru, Jordan: SPIs SG, AU, BH, CL, CO, MA, OM, PA, PE, JO respectively.

GSP is expired. The Generalized System of Preferences lapsed December 31, 2020 and has not been reauthorized through May 2026. CBP advises continuing to flag eligible imports with SPI "A" and pay column-1 duty during the lapse. If GSP is reauthorized retroactively, flagged entries become refundable. Post-importation GSP claims via Post-Summary Correction or protest are not allowed for entries during the lapse.

Rules of origin. An SPI claim confirms the rate is available; it does not verify the goods meet the program's rules of origin. RoO compliance is the importer's responsibility. Most programs use tariff-shift, regional-value-content, or specific-process tests defined in the agreement text or implementing regulations.

Worked example

A line item for steel screws from China.

Facts.

• HTS: 7318.15.80.66 (Cap screws of iron or steel)
• Country of origin: China (CN)
• Country of melt and pour: China
• Entry date: May 1, 2026
• Customs value (transaction value, ex-works, freight and insurance separately stated): $50,000
• Mode: ocean
• No SPI claim, not covered by an active 301 exclusion

Layer-by-layer build. Same shape you would see in the calculator: each line carries an authority badge, the regulatory citation, the rate, and the dollar amount contributed.

Effective rate before AD/CVD scope verification: 83.97% on a $50,000 invoice. Section 232 alone contributes 60% of the duty bill. Section 301 contributes 30%. The MFN base is just over 10%. MPF and HMF are rounding errors at this value, but they land on every entry regardless of duty layer.

Mandatory scope check

The Tandom calculator surfaces one heading-level AD/CVD advisory match on this entry: A-570-932, the AD order on Steel Threaded Rod from China. The match is flagged as "advisory" because it lines up at the 4-digit heading (7318) but not at the 8-digit subheading (7318.15.80 is cap screws, not threaded rod). Do not assess deposits on this advisory. Pull the order's Federal Register scope description and any subsequent Commerce scope rulings; cap screws are almost certainly outside the threaded-rod scope, but the broker owns that determination, not the calculator.

The general rule: if the calculator returns a heading-level AD/CVD match, the answer is "verify before assessing." If a scope ruling captures the importer's product, add the deposit rate (single-rate companies often see 50 to 200%, country-wide non-market-economy rates can exceed 200%).

USMCA flip example

The same nominal product, but Mexico-origin and qualifying under USMCA rules of origin. SPI "S" claim: MFN duty becomes "Free" under the USMCA preferential column, no Section 301 (different origin), MPF is waived for USMCA-originating goods. Section 232 still applies at 50% on steel content because Section 232 does not honor preference programs. The $50,000 line goes from $41,985.70 to about $25,062.50 (Section 232 50% plus HMF 0.125%, no MFN, no MPF, no 301). The savings are mostly the MFN-plus-301-plus-MPF stack, not the 232.

Common pitfalls

The mistakes that bite most often:

Country of origin vs. country of export

Origin is where substantial transformation last occurred. Export is where the goods last shipped from. Section 301 and AD/CVD apply by origin. A shipment trans-shipped through Vietnam from a Chinese factory is China-origin, not Vietnam-origin, regardless of routing. CBP audits trans-shipment aggressively.

Entry date vs. shipping date

The rate of duty is fixed at the time of entry per 19 CFR 141.69, not at export or arrival. A shipment exported under a 25% rate but entered after the rate increased to 50% pays 50%. The few exceptions are written into specific Executive Orders themselves.

Column 2 misclassification

Defaulting to MFN/Column 1 for Russia, Belarus, Cuba, or North Korea origin is a flat error. For Russia and Belarus, this has been wrong since April 2022.

Missing a Chapter 99 secondary code

A 7318 fastener from China entered without 9903.88.03 misses the 25% Section 301. Without 9903.82.x (post-April 2026) it misses Section 232. ACE will reject many of these but not all. CBP can issue a Notice of Action and demand the duty months later.

Quoting MFN-only and forgetting AD/CVD

Some commodity classes look ordinary at the HTS level but sit inside a live AD/CVD order: steel nails A-570-909, certain steel threaded rod, kitchen sinks, solar cells, pneumatic tires, hardwood plywood, citric acid, and many more. Always check Commerce's case calendar for the HTS code before quoting.

Section 232 derivative chapters where the add-on is non-obvious

A casual reader assumes 232 is just Chapters 72/73/76. The 2025 expansion reaches into Chapters 82 (tools), 83 (miscellaneous metal articles), 84 (machinery), 85 (electrical), and 87 (vehicle parts, specifically 8708.10.30 and 8708.29.21 on steel content). For these, content-value reporting and the metal-only Line 2 are not optional.

Section 301 exclusion certificates

An exclusion is product-specific and time-bounded. If the certificate's effective dates do not bracket the entry date, the certificate does not help. Some exclusions require the importer to be a specific named party. Always re-verify against the exclusion's FR notice, not a saved certificate.

First-sale-for-export eligibility

Three conditions: bona fide sale at the first tier, goods clearly destined for the US at that point, arm's-length pricing. If a middleman dictates factory pricing (common in related-party setups), the first-sale price is not arm's length and the lower price is not eligible. Documentation: complete purchase orders at every tier, transfer-pricing study, Incoterms confirmations.

Section 321 de minimis is gone

China-origin de minimis ended May 2, 2025. All-country de minimis ended August 29, 2025 by Executive Order. The One Big Beautiful Bill Act (signed July 10, 2025) permanently repeals 19 USC 1321 commercial de minimis effective July 1, 2027. Importers used to dropping under-$800 e-commerce shipments through Section 321 now formally enter and pay duty regardless of value or origin.

Aluminum smelt-and-cast "unknown" pays 200%

Effective June 28, 2025, declaring "unknown" on derivative aluminum forces the 200% Russia rate via 9903.85.67/.68. Brokers used to leaving smelt/cast blank now produce a 200% bill if the importer does not supply origin data.

MPF and HMF apply on top of every layer

MPF and HMF are user fees, not duties. They are computed at the entry-summary level (MPF capped, HMF uncapped on ocean) and are additive to whatever the duty stack produced. MPF can be waived by USMCA-originating goods, Israel FTA, AGOA-eligible goods, and a handful of others. Section 232, 301, and 122 exclusions never waive either fee.

Glossary

HTS / HTSUS

Harmonized Tariff Schedule of the United States, published and maintained by USITC. 10-digit codes; the first six digits are international (HS), the last four are US-specific statistical breakouts. Authoritative source: hts.usitc.gov.

MFN / Column 1 General

Most Favored Nation / Normal Trade Relations rate. The default rate for any WTO-member origin not subject to preference or trade remedy.

Ad valorem

By value. A percentage of customs value. Most modern duties are ad valorem.

Specific duty

Per unit (per kilogram, per liter, per piece). Common in agriculture and footwear.

Chapter 99

The HTSUS chapter that holds temporary trade-remedy provisions: Sections 232, 301, 201 safeguards, IEEPA (now expired), Section 122 (current). The 9903 four-digit prefix is reported as a secondary classification on the entry line.

Chapter 98

Special classification provisions: 9801 (US/foreign goods returned), 9802 (articles exported for repair, alteration, or processing; only the value of the work abroad is dutiable), 9803 (instruments of international traffic).

ACE

Automated Commercial Environment, CBP's entry-filing platform. All formal entries, PGA messages, and Chapter 99 reporting flow through ACE.

AD/CVD

Antidumping and Countervailing Duty. Trade-remedy duties on specific products from specific origins that Commerce has determined are dumped (sold below normal value) or subsidized. Cash deposits at entry, final assessment 12 to 18+ months later.

SPI

Special Programs Indicator. Single-letter or letter-plus code that flags a preference-program claim (S, S+, KR, JP, A, A+, D, E, R, IL, etc.).

Melt and pour

For steel, the country where the raw steel was first solidified into slab, billet, or ingot. Drives Section 232 country-specific rates.

Smelt and cast

For aluminum, the country where the metal was last liquefied and cast. Drives the 200% Russia rate at 9903.85.67/.68.

Scope ruling

Commerce determination clarifying whether a specific product is inside or outside the scope of an existing AD/CVD order. Usually requested by an importer, sometimes self-initiated by Commerce.

MPF

Merchandise Processing Fee. 0.3464% ad valorem on formal entries; fiscal year 2026 cap $33.58 minimum, $651.50 maximum, plus $4.03 if filed manually. Waived for USMCA-originating goods, Israel FTA, AGOA-eligible goods, and a few others.

HMF

Harbor Maintenance Fee. 0.125% ad valorem on ocean shipments only. No minimum or maximum.

Substantial transformation

The case-by-case test CBP applies to determine non-preferential country of origin: did processing in country X result in a new article with a different name, character, and use? Origin under preference programs uses tariff-shift or regional-value-content rules from the agreement text.

First sale for export

Valuation election allowing the importer to declare the factory-to-middleman price (lower) instead of the middleman-to-importer price (higher). Three conditions: bona fide sale, clearly destined for the US at that point, arm's-length pricing.

FAQ

High-intent questions brokers and importers ask most often.