How to Calculate US Customs Duty: FOB Valuation, HTSUS Codes & Formulas
Calculating import duties for commercial shipments entering the United States requires understanding the official transaction value method mandated by U.S. Customs and Border Protection (CBP). Unlike European and Commonwealth customs regimes that tax landed freight costs, the United States assesses tariffs strictly on the product's export value.
1. The Core Principle: FOB Transaction Value
Under federal law (19 U.S.C. § 1401a), the statutory primary basis of customs value is the Transaction Value—the price actually paid or payable for the merchandise when sold for exportation to the United States.
2. The 4 Components of a US Customs Entry Bill
When your commercial shipment clears U.S. Customs, the total assessment consists of up to four distinct government fees:
1. General (Column 1) MFN Tariff
The base duty rate established under the 10-digit Harmonized Tariff Schedule of the United States (HTSUS) for World Trade Organization (WTO) member countries. Can be zero (duty-free), ad valorem (a percentage like 3.5%), specific (e.g. $0.15/kg), or compound.
2. Section 301 Trade Remedy Surcharge
If your goods originate from China, they are likely subject to punitive Section 301 tariffs under lists 1, 2, 3, 4A, or 2024 revisions. These add 7.5%, 25%, or up to 50% directly on top of the base MFN tariff.
3. Merchandise Processing Fee (MPF)
A statutory federal user fee of 0.3464% of customs value. For formal entries (shipments valued > $2,500), MPF is subject to a statutory minimum floor (~$31.67) and a maximum ceiling (~$614.35).
4. Harbor Maintenance Fee (HMF)
Assessed at 0.125% of the customs cargo value strictly on commercial ocean freight arriving at US maritime ports. Air freight and border truck crossings are 100% exempt from HMF.
3. Worked Calculation Example
• Quantity: 2,000 units at $15.00 FOB price = $30,000.00 Customs Value
• HTSUS Code: 8504.40 (Power Supplies)
• Base MFN Tariff: 3.0%
• Section 301 List: List 3 (25.0%)
4. The $800 De Minimis Rule (Section 321)
Under 19 U.S.C. § 1321, commercial shipments imported by one individual or business on a single calendar day valued at $800.00 USD or less enter the United States duty-free and exempt from MPF. Note that this exemption cannot be intentionally split or manipulated to evade formal customs duties.
Primary Sources & Verified Guidelines
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