Tariff Stacking Rules 2026: Which US Tariffs Add Up

Tariff stacking is how several US tariffs combine on one import. By default, every Chapter 99 tariff that covers a product adds to the base rate. The main exceptions in October 2026: Section 301 China stacks on everything, including Section 232; the Section 301 forced-labor and Brazil tariffs switch off when a Section 232 duty applies; and since September 15, 2026, most Section 338 Canada duties stack on Section 232 too. Here's each rule and where it's written.

Do US tariffs stack? The default rule

When more than one tariff covers a product, the starting rule is simple: they stack. The base rate, plus each Chapter 99 tariff that applies, all charged on the same customs value.

The exceptions are written into the HTS itself, in two forms:

• Exemption headings that switch a tariff off in specific cases, like 9903.05.90, which removes the forced-labor duty from Section 232 goods.
• Non-stacking notes in the U.S. notes to Chapter 99, which say that one program doesn't apply to goods covered by another.

Below is how the programs in force in October 2026 combine.

Section 301 and Section 232: China stacks on everything

The Section 301 tariffs on Chinese goods (Lists 1 to 3 at 25%, List 4A at 7.5%, and the 2024 to 2026 increases of 25% to 100% on products like semiconductors, solar cells, EVs and medical gloves) apply on top of every other tariff.

That includes Section 232. A steel article from China in October 2026 pays the base rate, 50% under Section 232 and 25% under Section 301 List 3: 77.9% in total on HTS 7326.90.86.88. Our guide to how US tariffs are calculated works through that example line by line.

Country programs give way to Section 232

Three newer country-wide tariffs switch off when a Section 232 tariff applies to the product (Brazil from July 22, 2026, forced labor from July 24 and Canada from August 22):

"Section 232 goods" here means goods that actually pay one of the Section 232 duty headings: metals, autos and parts, heavy trucks, semiconductors, wood products or patented pharmaceuticals. Two things don't count:

• Exemptions from Section 232. A product that claims "contains no steel, aluminum or copper" (9903.82.01) isn't paying Section 232, so the forced-labor duty applies to it.
• The drone tariffs. Section 232 duties on unmanned aircraft (from September 3, 2026) aren't on the exemption lists, so the country programs still apply on top of them.

Tariffs that stack with each other

• Brazil: the 25% Section 301 Brazil tariff and the 12.5% forced-labor duty both apply, for 37.5% on top of the base rate on a non-exempt product.
• China: the Section 301 China list rate and the 12.5% forced-labor duty both apply, unless a Section 232 tariff applies.
• Canada: the 50% Section 338 tariff applies even with a USMCA claim. The 10% forced-labor duty for Canada drops off when the goods are claimed under USMCA (9903.05.93).
• Quartz: the Section 201 safeguard on quartz surface products (25% in quota, 50% over quota, from August 15, 2026) is cumulative with everything else, including Section 301 China and the forced-labor duty.

Inside Section 232: one program per product

Section 232 now covers seven product groups (metals, autos, heavy trucks, semiconductors, wood, pharmaceuticals and drones), and when a product could fall under more than one, the HTS notes pick a winner:

Within each program, the headings are mutually exclusive too: a metals product pays one of the 9903.82 headings, a pharmaceutical one of 9903.04.60 to .70, a drone one of 9903.08.21 to .26.

One catch: the auto and heavy truck parts tariffs often depend on a fact the importer has to confirm (that the part is for a vehicle). Until that's confirmed, an auto part made of steel still pays the metals tariff.

All-in rates: how the EU, Japan and other deals stack

The 2025 deals with the EU, Japan and South Korea were originally written into IEEPA headings, which ended on February 24, 2026. What survives lives inside the product and country programs, as all-in rates: the tariff tops the total duty up to a set level.

The drone rates for allies apply only when substantially all the critical components come from the US or allied countries; otherwise the 25% or 100% drone duty applies.

"All-in" means the tariff adds whatever brings base rate plus tariff to the level shown. On a product with a 4% base rate, a 15% all-in tariff adds 11%. If the base rate is already 15% or higher, it adds nothing.

How to check which tariffs stack on your product

For any product, walk the list in this order:

1. Does a Section 232 duty heading apply? If yes, the forced-labor, Brazil and Canada dairy-and-food tariffs are off.
2. If the goods are Chinese, add the Section 301 China rate for the product's list.
3. If no Section 232 duty applies, add the forced-labor rate for the country, the Brazil 25% for Brazilian goods, and any Canada 338 list the product is on.
4. For Canada lists (b)(1) and (b)(3), add the 50% even if Section 232 applies.
5. Apply all-in rates last, against the base rate.

It's a lot to hold in your head for one product, and impossible across a catalog. A calculator that shows each heading it applied, and each one it switched off with the reason, is the only practical way to be sure. The HTS Hero duty calculator does exactly that, and the latest US tariff changes tracks every rule as it moves.