US Tariff Stacking, Explained

Tariff stacking occurs when multiple tariffs apply to the same imported product under separate trade actions. For example, a car part from abroad might face a national security tariff under Section 232, plus an additional tariff targeting border issues. This creates cumulative duties that increase the product's final effective rate.

No. While some tariffs apply cumulatively, others are mutually exclusive. In late April 2025, Executive Order 14289 established rules governing cumulative application, often called "stacking" multiple tariffs on imported products. EO 14289 created a hierarchy where certain tariff regimes supersede others and cannot stack. However, not all regimes are covered by the order. The ones that are not covered by any rule can cumulatively apply on top of any other applicable tariff.

Hirerachy EO 14289 and subsequent CBP guidance introduce a structured framework determining the precedence and interaction of overlapping tariff measures. A recent Proclamation and related guidance issued on 3 June further introduced significant updates, particularly affecting steel and aluminium derivative products.

When an imported product faces Section 232 tariffs on auto or autoparts, it will NOT be subject to Section 232 tariffs on aluminium, Section 232 tariffs on steel, or IEEPA tariffs on imports from Canada or Mexico.

If a product faces Section 232 aluminium or steel tariffs but not auto or auto parts tariffs, it will NOT face IEEPA tariffs targeting Canada or Mexico. However, Section 232 steel and aluminium tariffs may apply concurrently to the same product.

The 3 June guidance states that Section 232 steel and aluminium tariffs and other additional tariffs can now apply to the same product based on its content. Section 232 tariffs now only apply to the steel and aluminium content of imported products. Non-steel and aluminium content faces applicable additional tariffs (for instance, reciprocal tariffs). Previously, Section 232 steel and aluminium tariffs applied to the full value of imported products containing those metals.

This change improves market access for foreign products by narrowing the Section 232 tariff scope to only metal components. As of early June 2025, these tariffs (50%) exceed others, such as current reciprocal tariffs (10%) (10%). Reducing the applicability proportion decreases the final effective rate.

Simultaneously, the measure expands the potential for other duties on non-metal portions previously exempt under Section 232. Under the original EO 14289 hierarchy, reciprocal tariffs did not apply to products already facing Section 232 tariffs (50%). This development could worsen market access for foreign products when additional duties exceed Section 232 rates, as occurred with China's reciprocal tariffs (125%) before the temporary suspension on 14 May 2025.

For all other cases, duties can fully stack:

• Unaffected by Hierarchy EO: General MFN tariff, Section 301 tariffs, Reciprocal Tariffs, trade defence actions are not affected by the EO 14289 and may still apply cumulatively.

• Steel and Aluminium Stacking: If a product is covered by both steel and aluminium tariffs, and is not subject to the auto or border-related tariffs, both Section 232 tariffs apply. Each tariff applying to their respective metal content. 

Table 1 summarises whether a tariff regime is subject to hierarchy rules or can be stacked:

Table 1 

Notes:

1. Current reciprocal regime tariffs are baseline 10% for all countries except Canada, Mexico, and USHTS Column II countries (Cuba, Belarus, North Korea, Russia). Higher country-specific tariffs for 57 jurisdictions were postponed until 9 July. 

2. Bilateral deals with the UK and China were reached under this regime.

3. Metal content faces metal-specific tariffs (Section 232); non-metal content faces reciprocal tariffs separately without stacking.