U.S. tariff architecture noted

The United States is now running a layered tariff system that reaches across countries and products, with more sector tariffs still on the table. (commonslibrary.parliament.uk) The House of Commons Library said a 10% tariff applies to most UK goods entering the United States, while product-specific tariffs hit sectors such as steel, aluminum, autos, lumber, and semiconductors. It said the Trump administration has imposed tariffs on most countries since taking office on January 20, 2025. (commonslibrary.parliament.uk; congress.gov) U.S. Customs and Border Protection said a 25% tariff on certain semiconductors and their derivatives took effect on January 15, 2026. The same agency’s January 2026 overview listed a 25% tariff on passenger vehicles and many auto parts, with separate Section 232 rates for metals and timber products. (cbp.gov) Congressional Research Service said President Trump used both the International Emergency Economic Powers Act and Section 232 of the Trade Expansion Act to raise tariffs in 2025, and it said more Section 232 investigations could still produce new sector duties. The report also said the administration released 12 framework statements with trading partners between April and December 2025. (congress.gov) That legal map shifted again on February 20, 2026, when the UK Parliament briefing said a U.S. Supreme Court decision changed the basis for several tariffs. The briefing said it remains unclear whether the 10% tariff on most UK goods will be maintained or altered under the new framework. (commonslibrary.parliament.uk) The White House opened another front on April 2, 2026, when it announced tariffs of up to 100% on patented pharmaceutical products and ingredients under Section 232. A White House fact sheet said the tariffs take effect in 120 days for certain large companies and 180 days for smaller companies. (whitehouse.gov) For the UK, that pharmaceutical move came with a carveout. The Federal Register notice said patented pharmaceutical products and ingredients from the United Kingdom face a 10% tariff that can fall to zero under a future U.S.-UK agreement on drug pricing. (federalregister.gov) The U.S. Trade Representative on April 2 announced a pharmaceutical pricing arrangement with the UK, while the House of Commons Library said the broader U.S.-UK Economic Prosperity Deal announced on May 8, 2025 was only partly implemented as of mid-April 2026. The same briefing said the deal could remove the current 25% tariff on UK steel and aluminum if the UK meets U.S. supply-chain security requirements. (ustr.gov; commonslibrary.parliament.uk) Tax Policy Center said the Supreme Court struck down the International Emergency Economic Powers Act tariffs in February 2026, but other Trump tariffs remained in place. It said the administration’s tariff changes announced through December 4, 2025 would impose an average burden of about $1,050 per household in calendar year 2026. (taxpolicycenter.org) The result is a U.S. tariff system built from overlapping country rules, sector rules, court changes, and deal-by-deal exceptions. Exporters now have to track not just one tariff rate, but which law, product list, and bilateral arrangement applies on a given shipment. (commonslibrary.parliament.uk; cbp.gov; congress.gov)