How U.S. tariffs are set and changed

U.S. tariffs are imposed and changed under trade remedy laws that different agencies administer. The U.S. Department of Commerce’s Bureau of Industry and Security (BIS) describes Section 232 tariffs that follow national security investigations and presidential proclamations. The Office of the U.S. Trade Representative (USTR) lists Section 301 investigations that can lead to tariff actions, and U.S. Customs and Border Protection (CBP) lists and links to guidance and Federal Register notices that implement those actions at the border.

Who does what

BIS states that on March 8, 2018, the President exercised authority under Section 232 of the Trade Expansion Act of 1962 to impose tariffs on imports of steel and aluminum articles to protect national security, following Section 232 investigations led by BIS. BIS lists key presidential proclamations related to implementation and adjustments of these measures and links to Federal Register notices with consolidated lists of Harmonized Tariff Schedule of the United States (HTSUS) classifications subject to the tariffs as of March 2025.

USTR’s Section 301 page lists investigations into acts, policies, and practices of various economies. The page provides initiation dates and topics for these investigations, including matters related to intellectual property, digital services taxes, labor and human rights, and sector‑specific issues.

CBP states it is “enforcing new trade remedy measures for duties and quotas on imported goods.” CBP’s Trade Remedies page compiles links to operational guidance and Federal Register notices for Section 232 and Section 301 measures, and also lists actions under Section 338 concerning additional duties on certain goods of Canada.

How Section 232 tariffs are imposed and adjusted

According to BIS, presidential proclamations impose and adjust Section 232 tariffs after BIS investigations into national security effects of imports. BIS cites proclamations that apply tariffs to steel and aluminum and to certain downstream, or “derivative,” products, with duties calculated either on the full value of the product or on the value of the steel or aluminum content depending on the HTSUS classification.

BIS explains that the proclamations required the Secretary to establish a process to consider public requests for including new derivative aluminum and steel articles within the scope of the Section 232 tariffs. BIS publicized a rule on April 30, 2025 implementing the Section 232 inclusions process, and says submissions are accepted in two‑week windows three times per year. BIS provides a link for filing requirements and notes that submitted inclusion requests are posted on Regulations.gov to Docket BIS‑2025‑0023.

BIS also states that, effective 11:59 p.m. Eastern Time on Feb. 10, 2025, Commerce stopped processing Section 232 exclusion requests and is no longer accepting or issuing exclusions from the Section 232 steel and aluminum tariffs. Exclusions already granted and activated as of Feb. 10, 2025 remain effective until their expiration date or until their excluded volume is exhausted, whichever occurs first. BIS notes that all General Approved Exclusions and country‑level “alternative arrangements” were revoked effective March 12, 2025, and that the Section 232 Exclusions Portal remains online in read‑only mode to administer previously granted exclusions.

How Section 301 tariffs are initiated and changed

USTR’s Section 301 page lists investigations it has initiated, with topics and dates, such as investigations related to technology transfer and intellectual property, digital services taxes, currency, timber, labor and human rights, sectoral capacity, and other issues. These investigations are the basis for actions that can include additional duties.

CBP’s Trade Remedies page compiles Federal Register notices and CBP operational messages for Section 301 measures. For actions related to China, CBP lists repeated notices over multiple years titled as modifications, product exclusion notices, extensions of exclusions, and conforming or technical amendments. CBP also lists notices for Section 301 actions involving other economies, including Brazil and actions related to the failure to prohibit imports of goods produced with forced labor, with Federal Register citations and dates.

According to CBP’s listings, changes to Section 301 measures are communicated in the Federal Register through actions titled as modifications, product exclusions, extensions of exclusions, and conforming or technical amendments. CBP also issues CSMS guidance that explains filing practices, coding, and timing for the trade community.

How changes are communicated and applied at the border

BIS points to Federal Register notices that identify HTSUS classifications covered by Section 232 measures and provides contacts and links related to the inclusions process and the read‑only exclusions portal. BIS also links to consolidated HTSUS lists for Section 232 steel and aluminum as referenced in Federal Register notices.

CBP’s page consolidates Section 232 and Section 301 resources in one place. For Section 232, CBP lists guidance and Federal Register notices for metals, automobiles and parts, medium‑ and heavy‑duty vehicles and parts, semiconductors, timber and lumber, pharmaceuticals, unmanned aircraft systems, copper, polysilicon, and other categories noted on the page. CBP also highlights the Consolidated Administration and Processing of Entries (CAPE) tool in the Automated Commercial Environment (ACE) for IEEPA duty refunds and links to other tools and resources.

Other authorities shown on CBP’s page

CBP’s Trade Remedies page lists actions titled as Section 338 measures on certain goods of Canada. The page links to multiple Federal Register notices imposing, modifying, further modifying, or excluding certain Canadian products, with citations and dates.

Across these authorities, BIS describes the Section 232 investigation and proclamation process, USTR lists Section 301 investigations that can lead to actions, and CBP compiles the operational guidance and Federal Register notices that show how tariff measures are implemented and changed at the border.