Section 232 of the Trade Expansion Act of 1962 lets the President restrict imports on national security grounds, and the steel and aluminum tariffs imposed under it in 2018 were the first use of that authority at scale. The rates were 25 percent on steel and 10 percent on aluminum, then both rose to 25 percent in February 2025, and Proclamation 10947 of June 3, 2025 raised both to 50 percent effective June 4, 2025. Copper joined at 50 percent on August 1, 2025.
The United Kingdom is the exception that proves the rule. Under the US-UK Economic Prosperity Deal, UK steel and aluminum carry 25 percent instead of 50. Every other origin pays the full rate, and Section 232 has no statutory expiration date, so the rate stays until a proclamation changes it.
The rate is the number everyone quotes, and it is the less important number. The April 2026 proclamation changed the base the rate applies to, and the base decides the bill.
Before April 2026, the duty applied to the metal content of the product. A machine that was 20 percent steel by value paid 50 percent on the steel portion, and the other 80 percent of the value was untouched. The April 2026 proclamation, signed April 2 and effective April 6, changed that: duties now apply to the full customs value of products containing the affected metals, including copper, which was added to the same treatment.
The new system is tiered. Annex I-A carries 50 percent on the full value for primary steel, aluminum, and copper articles and closely related derivatives. Annex I-B carries 25 percent on the full value for certain derivatives. Lower tiers run 10 to 15 percent for goods with heavy US-sourced content or in specific relief categories, and products with less than 15 percent metal content are exempt.
The arithmetic is blunt. A $10,000 machine with $2,000 of steel content paid $1,000 under the old content-based rule. Under the new rule, at the 50 percent tier, it pays $5,000. At the 25 percent tier it pays $2,500. The derivative rate is lower, but it applies to five times the base, so the duty paid can be higher than it was at the top rate on content alone.
First, the annex. The tier is decided by the product's listing in the proclamation's annexes, not by the importer's reading of the metal content. A product that moved from Annex I-A to a relief tier in the June 2026 update, which widened the 15 percent tier to agricultural equipment, HVAC systems, and more industrial machinery, pays a different rate from the one it paid in May.
Second, the USMCA status. The tariffs do not replace rates in existing agreements, and USMCA-qualifying goods keep their treatment. A product that qualifies under USMCA is not subject to the Section 232 stack on the qualifying portion, which is the single largest saving available to most importers.
Third, the stacking. Section 232 sits on top of the MFN base rate and any Section 301 duties, and the rates are additive, not alternative. A product with a 9.8 percent MFN rate, a 25 percent Section 301 duty, and a 50 percent Section 232 duty pays 84.8 percent, and the entry summary has to carry each line separately. CBP announces the changes through CSMS messages, and reading them before the shipment lands is the difference between a planned cost and a surprise.
Fifty percent since June 4, 2025, for most origins, with the United Kingdom at 25 percent under the US-UK Economic Prosperity Deal. Copper joined at 50 percent on August 1, 2025.
It changed the tax base from metal content to the product's full customs value, and introduced tiers from 10 to 50 percent. A product with 20 percent steel content now pays on 100 percent of its value, so the duty can be higher at a lower tier rate than it was at 50 percent on content alone.
Products with less than 15 percent metal content are exempt from the Section 232 duties under the recast. The exemption is decided by the metal content, but the rate, once it applies, is on the full value.
Yes. The rates are additive: MFN base plus Section 301 plus Section 232, plus any antidumping or countervailing duties where they apply. Each line is reported separately on the entry summary.