The tariff calculation layers
Import tariff calculation is not a single step — it is a stack of layers that build on each other. The base layer is the customs value. The first tariff layer is the base duty rate from the HS/HTS code. Additional tariff layers may be added for specific origins or products. Tax and VAT are added on top. Brokerage and handling fees are charged separately.
- Layer 1: Customs value — the assessment base for all duty calculations.
- Layer 2: Base duty rate — from the HS/HTS classification.
- Layer 3: Additional tariffs — Section 301, Section 232, antidumping (where applicable).
- Layer 4: VAT or sales tax — applied by the destination country on the customs-value-plus-duties base.
- Layer 5: Brokerage and handling fees — charged by the carrier or broker separately.
Layer 1: Customs value
Duty is calculated on the customs value of the shipment. Customs value is typically the transaction value — the price paid for the goods, plus additions such as freight and insurance where applicable under the Incoterms used. The WTO Valuation Agreement governs how customs value is determined in most countries.
- Transaction value is the most common customs valuation method.
- Freight and insurance may be added to customs value depending on the Incoterms.
- Assists, royalties, and proceeds from resale may also affect customs value.
- Verify the correct customs value basis before calculating duty.
Layer 2: Base duty rate
The base duty rate comes from the HS code (or US HTS code for US imports). The duty rate is typically an ad valorem rate — a percentage of the customs value. Some products use specific rates — a fixed amount per unit of measurement. The duty rate varies by product from 0% to 37.5% or more.
- Ad valorem: a percentage of the customs value (e.g., 6.5%).
- Specific: a fixed amount per unit (e.g., $0.17 per kilogram).
- Compound: a combination of ad valorem and specific rates.
- The base duty rate applies when no preferential trade program is claimed.
Layer 3: Additional tariffs
In addition to the base duty, some imports are subject to additional tariffs that layer on top. Section 301 additional tariffs apply to products from China under unfair trade investigations. Section 232 surcharges apply to steel and aluminum products. Antidumping and countervailing duties apply when dumping or illegal subsidization is found. Additional tariffs are added to the base duty — they do not replace it.
- Section 301: additional tariffs on China-origin goods at the 9903 HTS chapter level.
- Section 232: surcharges on steel and aluminum products and derivatives.
- AD/CVD: antidumping and countervailing duties when dumping is found.
- Additional tariffs are calculated on the same customs value as the base duty.
Layer 4: Tax and VAT
After duties and additional tariffs are calculated, the destination country may apply a VAT (value-added tax) or sales tax on the import. In the EU, import VAT is applied to the customs value plus all duties. In the UK, import VAT applies on the same basis. Tax treatment varies significantly by country — some have a de minimis threshold below which no tax is charged.
- EU: import VAT applied to customs value plus all duties.
- UK: standard rate VAT applied to customs value plus all duties.
- Canada: federal GST (5%) plus provincial HST in some provinces.
- De minimis: many countries have a threshold below which no import tax is charged.
Layer 5: Brokerage and handling fees
The carrier or customs broker charges a separate fee for processing the customs entry. This fee is not part of the tariff calculation but is part of the total landed cost. Brokerage fees vary by carrier and by shipment value. These fees are typically charged regardless of whether additional tariffs apply.
- Carrier brokerage fee: charged for filing the customs entry on your behalf.
- Disbursement fee: charged when the carrier pays duties on your behalf and adds the amount to your bill.
- Brokerage fees are not part of the tariff calculation — they are separate charges.
- Factor brokerage fees into total landed cost estimates.
The full tariff calculation formula
Formula:
Customs Value x Base Duty Rate = Base Duty
Customs Value x Section 301 Rate = Section 301 Duty (if applicable)
Customs Value x Section 232 Rate = Section 232 Duty (if applicable)
Base Duty + Section 301 + Section 232 = Total Duty Estimate
Total Duty + Brokerage Fee = Total Additional Cost Estimate
Note: VAT/sales tax is applied in the destination country on the customs-value-plus-duties base (customs value + duties). This formula is for preparation use only — verify all rates in official sources before filing.Total landed cost for a US import can be estimated as follows. Customs value is the transaction value or CIF value depending on the Incoterms. Base duty equals customs value multiplied by the base HTS duty rate. Section 301 duty (if applicable) equals customs value multiplied by the Section 301 rate. Section 232 duty (if applicable) equals customs value or weight multiplied by the Section 232 rate. Total duty equals base duty plus Section 301 plus Section 232. Brokerage and handling are added separately. This estimate is for preparation use only — verify the applicable rates in USITC HTS before making business decisions.