On May 28, 2026, Commerce and the Office of the U.S. Trade Representative jointly published a notice amending the Harmonized Tariff Schedule of the United States (HTSUS) to implement part of a trade-and-security understanding with Taiwan. For anyone tracking the semiconductor supply base, the headline is less about what changed and more about what the U.S. chose not to change yet. The notice implements a January 15, 2026 memorandum of understanding (MOU) signed by the American Institute in Taiwan (AIT) and the Taipei Economic and Cultural Representative Office (TECRO), but it pointedly does not implement the broader reciprocal-trade agreement the two sides signed in February. The distinction is the story.
The legal architecture sits under Executive Order 14346, issued September 5, 2025, which authorized Commerce and USTR to implement framework or final trade-and-security agreements tied to the reciprocal-tariff national emergency (EO 14257) and to Section 232 of the Trade Expansion Act of 1962. The MOU's concrete tariff effects, as described in the notice, are bounded: modifications to Section 232 tariffs on automobile parts, timber, lumber and wood derivative products of Taiwan, plus removal of derivative Section 232 steel, aluminum, and copper tariffs from Taiwanese aircraft components. Those line items are not chips. But the framework they sit inside is the same one through which any future tariff treatment of Taiwan-origin semiconductors and equipment would flow.
"The Secretary and Trade Representative are taking necessary and appropriate action to implement the MOU at this time. The Secretary and Trade Representative are not implementing the ART at this time as it has not yet entered into force."— Federal Register, source
Why the MOU-versus-agreement split matters
The notice draws a clean line between two instruments. The MOU, signed January 15, 2026, is being implemented now. The Agreement on Reciprocal Trade (the "ART"), signed February 12, 2026, is not — because, in the notice's own words, it "has not yet entered into force." For risk modeling, that sequencing is the most actionable fact in the document. It tells you that the U.S.-Taiwan trade relationship is being normalized in stages, with the narrower tariff carve-outs landing first and the comprehensive reciprocal framework still gated behind a procedural step. Companies with Taiwan-origin exposure cannot assume the full agreement's terms are in effect; only the MOU's enumerated modifications are.
That staging also frames the negotiating posture. The MOU explicitly committed the United States to modify Section 232 tariffs "in certain respects," and this notice executes the first tranche. The effective-date mechanics underscore how live the changes are: the notice itself took effect May 28, 2026, but the HTSUS modifications in the Annex apply to goods entered for consumption, or withdrawn from warehouse, on or after 12:01 a.m. eastern time on May 1, 2026 — a retroactive entry date that importers' customs and duty-drawback teams have to reconcile against entries already filed.
The chip-relevant read: it's about the channel, not the line items
No semiconductor tariff line moves in this particular notice. The directly affected goods are automobile parts, timber and wood derivatives, and metals-derivative aircraft components. So why does it belong on a chip desk? Because Taiwan is the single most important node in the global semiconductor supply chain, and the mechanism being exercised here — EO 14346 plus Section 232 — is the same statutory vehicle the United States has used to threaten and modulate tariff treatment of chips and chipmaking. A Section 232 investigation into semiconductors operates under the identical authority. When Washington establishes the procedural plumbing for staged, MOU-then-agreement implementation with Taipei, it is building the channel through which any future semiconductor-specific tariff relief or imposition would be administered.
The selective implementation also reveals leverage management. By implementing the MOU's metals and autos-parts relief while holding the comprehensive agreement in reserve, the U.S. retains a bargaining chip over the larger reciprocal-trade terms. For Taiwan's industrial base — and for the U.S. firms that depend on it — that means the tariff environment is explicitly provisional. The notice's language that the ART is not being implemented "at this time" is a forward-looking flag: the rest of the package remains contingent.
What the record shows
Three points are firmly on the record. First, the United States has begun implementing its trade-and-security understanding with Taiwan, effective May 28, 2026, but only through the January MOU, with the HTSUS changes reaching back to entries on or after May 1, 2026. Second, the concrete tariff modifications are confined to automobile parts, timber and wood derivatives, and the removal of derivative steel, aluminum, and copper Section 232 tariffs from Taiwanese aircraft components. Third — and most important for forward planning — the broader February reciprocal-trade agreement has not entered into force and is not being implemented, leaving the comprehensive terms unresolved.
It is also worth noting how the relief is targeted. The MOU's tariff modifications concentrate on inputs and components — automobile parts rather than finished vehicles, derivatives rather than primary metals, aircraft components rather than aircraft. That input-level focus is characteristic of agreements designed to lower costs in integrated North American and trans-Pacific manufacturing without conceding on the headline trade balance. For firms that assemble hardware using Taiwan-sourced subcomponents, the relevant question is always whether their specific inputs fall inside the Annex's modified lines, which is why the technical schedule, not the announcement, governs the actual duty outcome.
For a supply-chain risk team, the instruction is to treat the U.S.-Taiwan tariff relationship as a moving, staged process administered under EO 14346 and Section 232 authority, not a settled state. The semiconductor line items are not in this notice, but the regulatory machinery that would carry them is now demonstrably operational. Watching for the next notice — the one that implements the ART once it enters into force — is the way to anticipate where Taiwan-origin chip and equipment treatment lands.