Section 301 Investigations Reshape Global Expansion Strategy: "Substantial Transformation" Becomes the Key Test for Vietnam Manufacturing

1. The U.S. launches three Section 301 investigations targeting Vietnam

According to the China Council for the Promotion of International Trade (CCPIT) Commercial Legal Service Center and multiple legal research institutions, the Office of the United States Trade Representative (USTR) initiated three separate Section 301 investigations involving Vietnam between March and May 2026, significantly increasing compliance pressure.

On March 11, USTR launched a Section 301 investigation into structural overcapacity in manufacturing, alleging that Vietnam and 15 other major trading partners maintain excess industrial capacity that distorts U.S. commerce.

On March 12, USTR initiated a forced labor Section 301 investigation covering 60 economies worldwide. Under the preliminary determination released on June 2, Vietnam is subject to an additional 12.5% tariff, which could take effect as early as July 2026.

On May 29, following the publication of the 2026 Special 301 Report on April 30, USTR officially designated Vietnam as a Priority Foreign Country and launched an intellectual property Section 301 investigation. This marks the first time in 13 years that a country has received this highest-level designation. The investigation focuses on five areas: online piracy enforcement, counterfeit goods enforcement, border enforcement, unauthorized software usage, and cable/satellite signal theft.

Under U.S. law, USTR must issue a final determination within six months, meaning Vietnamese exports to the United States could face additional tariffs or other trade restrictions by November 29, 2026.

2. "China components + Vietnam assembly" model faces tougher substantial transformation review

Over recent years, many Chinese manufacturers have relocated production to Vietnam, creating a supply chain model of Chinese components → Vietnam assembly → U.S. export.

When determining country of origin, U.S. Customs and Border Protection (CBP) applies the Substantial Transformation doctrine, assessing whether manufacturing in Vietnam fundamentally changes the product's name, character, or use.

If only simple assembly, testing, packaging, or labeling is completed in Vietnam while key components—such as PCBs, plastic molded parts, connectors, semiconductors, and stamped metal parts—remain Chinese-made, CBP may continue to classify the products as Made in China.

Legal and consulting firms note that U.S. enforcement is shifting from document verification to full supply-chain scrutiny through:

• Production process verification;
• Local value-added assessment (generally requiring 40–45% local value addition);
• Bill of Materials (BOM) traceability covering the origin of key components.
  

Importers unable to provide complete procurement records, production documentation, or cost structures may face cargo detention and additional duties.

3. Three categories of Vietnam-made products face the greatest compliance risks

Based on USTR investigations and industry analysis, three categories face elevated risks:

First, products involving only simple assembly in Vietnam while core manufacturing and value creation remain in China.

Second, products within U.S. trade-sensitive industries, including steel, aluminum, solar products, batteries, automotive parts, semiconductors, industrial machinery, chemicals, and plastics.

Third, products lacking complete supply-chain traceability. U.S. buyers increasingly require suppliers to verify raw material sources, manufacturing processes, local value-added ratios, labor compliance, and intellectual property compliance.

4. Vietnam also tightens origin verification

Meanwhile, Vietnam has strengthened its own customs enforcement.

In early July 2026, Vietnam Customs issued Official Letter No. 17552/CHQ-GSQL, placing 18 categories of goods under enhanced origin verification and anti-transshipment controls.

The new measures require stricter examination of certificates of origin for imported components from China and other Asian countries, establish high-risk enterprise watchlists, and strengthen supervision over relabeling and repackaging activities in bonded warehouses.

Violations may result in fines, suspension of customs clearance privileges, or criminal liability under Vietnamese law.

Industry Perspective

The latest U.S. Section 301 investigations indicate that compliance reviews are evolving from simple origin declarations to comprehensive supply-chain verification.

For Chinese manufacturers expanding into Vietnam, relocating production alone is no longer sufficient. Companies should establish robust evidence covering BOM traceability, local value-added calculations, manufacturing processes, labor compliance, and origin documentation to prepare for future customs inspections and customer due diligence.