The US Department of Commerce ( DoC ) has announced steep preliminary anti-dumping duties on vehicle chassis and chassis parts imported from Vietnam,  Mexico and Thailand in a move aimed at protecting domestic manufacturers from what it deems unfairly priced competition.

Vietnam is bearing the brunt of the decision, with a duty rate of 511.16%, a record high for Vietnamese heavy industrial products targeted in US trade cases. Mexico and Thailand also face significant tariffs, though at lower levels.

Vietnam singled out

The DoC concluded, according to a notice published in the Federal Register, the daily journal of the US government, that chassis producers from all three countries had sold their products in the US market at less than “fair value”.

For Vietnam, the decision is particularly severe. The DoC investigated two companies – Thaco Special Vehicles Manufacturing and Thaco Industries Trailers and Heavy Steel Structures – but treated them as a single entity, referred to collectively as Thaco, which, the DoC notes, was the only Vietnamese exporter examined during the probe.

Despite this, the massive 511.16% preliminary duty will not only apply to Thaco, but to every other Vietnamese exporter of vehicle chassis and chassis parts not individually reviewed. This means that all shipments of such products from Vietnam to the US will face the same prohibitive tariff, at least until a final ruling is issued.

Trade observers say the scale of the penalty is unprecedented. “This is among the harshest duties ever applied against Vietnam’s industrial exports,” points out a trade consultant in the export-driven Southeast Asian nation, who asked not to be named.

Mexico, Thailand also targeted

Mexico, another key exporter, was hit with a 32.37% preliminary anti-dumping duty. However, because the DoC had already imposed a 133.18% countervailing duty on Mexican chassis, the combined rate remains at 133.18%.

Thailand’s exporters face a more varied outcome. Preliminary anti-dumping duties range from 46.12% to 181.57%, depending on the company, alongside countervailing duties between 2.24% and 9.42%. The combined tariff burden, therefore, falls between 48.36% and 190.99%, creating substantial uncertainty for Thai exporters.

With the ruling now in effect, US Customs and Border Protection will suspend liquidation of all incoming shipments covered by the order. Importers will be required to post cash deposits matching the preliminary duty rates.

Extension to 2026

The duties are preliminary, the DoC notes, and subject to change. A final determination is scheduled for December 2025, but it could be delayed until February 2026.

Thaco of Vietnam, with its production hub located in Danang on the central coast, has already requested an extension, which the DoC has approved. As a result, the provisional duties will remain in place for up to six months instead of the usual four, with the final decision expected no later than mid-February 2026.

The US Chassis Manufacturers Coalition, which includes major American chassis manufacturers Stoughton Trailers and Cheetah Chassis Corporation, applauded the DoC’s preliminary anti-dumping duties. “The significant preliminary duties,” states Robert E. DeFrancesco, the coalition’s trade attorney, “show that the US chassis industry faces significant unfair competition from multiple sources that only trade relief can prevent.”

The industry has already seen a series of cases against Chinese exporters, which resulted in both anti-dumping and countervailing duties. The latest investigation shifts attention to Vietnam, Mexico and Thailand.

What happens next

The process is not over yet. The DoC will continue gathering and verifying data from exporters and importers while also reviewing counter-arguments submitted by foreign companies and governments.

After the DoC issues its final determination, the case will move to the US International Trade Commission ( ITC ), which will assess whether the imports from Vietnam, Mexico and Thailand have caused “material injury” or pose a threat of injury to the US chassis industry.

If the ITC finds evidence of injury, the duties will become permanent and remain in force for years. If not, the case will be terminated, and duties collected in the interim will be refunded.