Section 338 Tariffs on Canada: What Importers Need to Know Before August 19

On July 20, 2026, President Trump signed three proclamations under Section 338 of the Tariff Act of 1930 (19 U.S.C. § 1338), a statute that has been on the books since the Smoot-Hawley era but hasn't been used to impose tariffs in roughly 80 years. The duties take effect August 19. If you import from Canada, you have about 18 days to determine whether your goods are in scope and what your stacked duty rate will actually be.

The headline rate is 50% additional ad valorem on top of every applicable duty already owed. It stacks on the base MFN rate, on the Section 301 forced labor tariff that took effect July 24, on AD/CVD orders. And unlike the now-vacated IEEPA tariffs on Canada, USMCA origination provides no relief. USMCA-qualifying Canadian goods pay the Section 338 duty the same as everything else.

What Section 338 Is and Why It Matters Now

19 U.S.C. § 1338 authorizes the President to impose additional duties of up to 50% on imports from a country that discriminates against US commerce by treating imports from another country more favorably than US imports. The mechanism requires no ITC investigation, no notice-and-comment rulemaking, and no congressional approval. The President makes a discrimination finding, issues a proclamation, and duties take effect 30 days later.

No modern court has interpreted Section 338. The statute has been dormant long enough that its constitutionality in the current legal environment is an open question, but unlike IEEPA, which the Supreme Court struck down in February 2026 in Learning Resources, Inc. v. Trump, No. 24-1287, Section 338 is a purpose-built tariff retaliation mechanism, not an emergency economic powers statute repurposed for trade policy. Legal challenges have been filed, but no court has stayed the August 19 effective date as of this writing.

The administration's decision to invoke Section 338 follows directly from the IEEPA ruling. Canada's previous tariff layer under IEEPA was vacated along with everything else in that decision. Section 338 is the replacement.

The Three Proclamations and What Triggered Them

Each proclamation cites a specific Canadian discriminatory practice. The product scope of each doesn't necessarily map neatly onto the named sector.

Motor vehicles. Canada's surtax on US-manufactured automobiles, imposed during prior trade disputes, is the stated justification. The product scope, however, covers 439 tariff lines that don't include actual automobiles or automobile parts. Both categories are excluded from Section 338 because they already carry Section 232 tariffs, and the proclamations carve out Section 232 goods. What the motor vehicles proclamation actually covers is a broad set of goods spanning HTS Chapters 84 (machinery), 85 (electrical equipment), 94 (furniture, including car seat parts), and consumer goods across other chapters. Cement, plywood, furniture, hockey sticks, fishing rods, swimming pools, seeds, clothing, and wigs are among the covered product categories. By import value, this proclamation represents the substantial majority of the Section 338 scope.

Alcoholic beverages. Several Canadian provinces maintain listing restrictions and distribution policies that effectively exclude US alcohol from provincial retail markets while permitting Canadian products to sell freely. The proclamation covers beer, wine, cider, fermented beverages, and distilled spirits.

Dairy. The dairy tariff-rate quotas (TRQs) that Canada negotiated with the European Union under CETA (the Canada-EU Comprehensive Economic and Trade Agreement) provide more favorable market access than the TRQs Canada agreed to for US producers under USMCA. That differential forms the discrimination finding. Approximately 52 HTSUS subheadings are covered: fluid milk, cream, whey, lactose, casein, and related products.

The three proclamations are published in the Federal Register, with Annex I to each proclamation listing the covered 8-digit HTSUS subheadings. That's the definitive coverage list, not news summaries. USTR's official statement on the action summarizes each discrimination finding alongside the legal authority.

What's Excluded

The categorical exclusions matter because the motor vehicles proclamation sweeps in products most importers wouldn't expect from a "motor vehicles" tariff action. If your goods fall in an excluded category, Section 338 doesn't apply regardless of HTS chapter.

Excluded:

Energy products (crude petroleum, refined products, LNG, coal)
Potash
Fish and seafood
Critical minerals
Goods already subject to Section 232 measures: steel (25%), aluminum (10%), copper, and specifically automobiles and automobile parts
Products covered by the WTO Agreement on Trade in Civil Aircraft (except unmanned aircraft)

There's no exclusion request process. The 2018 Section 301 tariffs on Chinese goods created a product-exclusion portal and produced thousands of product-specific exemptions. Section 338 has no equivalent mechanism. The proclamations don't authorize a process for importers to seek relief on specific products. The categorical exclusion list is the only avenue out.

USMCA Won't Save You

This is the point that needs to be stated plainly. Canada's IEEPA tariffs, which ran from early 2025 until the Supreme Court decision, had a USMCA carve-out. USMCA origination was a meaningful defense against that duty layer. Importers spent real money documenting USMCA rules of origin compliance precisely to preserve that carve-out.

Section 338 applies to "goods of Canada" with no exception for USMCA-qualifying goods. A certificate of origin, a fully documented tariff shift analysis, a properly executed CBP Form 434: none of it provides relief under Section 338. USMCA-qualifying Canadian wine, USMCA-qualifying Canadian dairy, USMCA-qualifying Canadian machinery parts: all covered by the 50% additional duty if the HTS subheading appears in one of the three proclamation annexes.

The only path out of Section 338 coverage is for the good to fall within one of the categorical exclusions listed in the proclamations themselves. Canada's existing trade framework with the US and USMCA preferential rules are beside the point.

What the Stack Actually Looks Like

For covered Canadian-origin goods, the effective duty rate is the sum of all layers. Nothing offsets anything else.

Consider Portland cement (HTS 2523.29.00), explicitly listed in the motor vehicles proclamation annexes. The Column 1 general rate is free. As of July 24, Canada's Section 301 forced labor tariff adds 10%. Come August 19, Section 338 adds another 50%.

Total for Canadian cement entering on or after August 19: 60%.

On a shipment of 500 metric tons at $150/MT (a reasonable bulk price for Portland cement), the duty cost is $45,000 on a cargo that previously entered free. Infrastructure project managers and building materials importers sourcing from Canadian producers need to run these numbers now, not after the first entry liquidation.

Canadian spirits provide another illustration. A duty stack before July 24 was the Column 1 rate on the applicable distilled spirits subheading. After July 24, add 10% for Section 301 forced labor. After August 19, add 50% for Section 338. Importers who locked in pricing with Canadian distilleries for Q3 delivery windows are looking at landed costs that are materially different from what they modeled in Q1.

For goods already subject to an AD/CVD order, Section 338 stacks on that too. The additional 50% is calculated on the dutiable value, separate from and additive to cash deposit rates.

What to Do Before August 19

Map your HTS codes against the proclamation annexes. Start with Annex I of each proclamation in the Federal Register. The motor vehicles proclamation (document 2026-14997) is the broadest in scope. Check every 8-digit HTSUS subheading in your Canadian import program against all three lists. Don't assume the sector name predicts the product scope. Cement is in the motor vehicles proclamation.

Identify goods currently in production or transit. Section 338 duties apply to goods "entered for consumption or withdrawn from warehouse for consumption on or after 12:01 a.m. ET on August 19, 2026." For goods already loaded on a vessel, the in-transit question turns on when they entered for consumption. Talk to your broker about timing options on any shipments currently moving.

Confirm your Section 232 exclusion status. If you import Canadian steel, aluminum, copper, or actual automobile parts, you're excluded from Section 338. But that exclusion only applies if the classification is correct. If goods that qualify as Section 232 products have been entered under broader or incorrect HTS subheadings, fix that now, not after an audit flags the discrepancy.

Recalculate landed costs for every covered product line. The landed cost calculator shows the full tariff stack by HTS code and origin. For Canadian-origin goods in scope, recalculate with the 50% Section 338 layer included to confirm actual exposure. For lines where the stacked rate materially changes your economics, run the same calculation for alternative sourcing origins via the HTS lookup tool to compare landed costs across countries.

Review your continuous transaction bond. Customs bonds are sized based on annual duty liability. A 50% additional duty on a meaningful Canadian import program is a large step-change in duty exposure. Bond insufficiency notices from CBP require a response within 30 days and can create filing disruptions. Calculate the projected new duty load and confirm your bond covers it before August 19.

Talk to your Canadian suppliers. Section 338 changes the negotiating dynamics on any open purchase order or pricing discussion. Suppliers whose goods will carry a 50%-plus duty increment have a strong incentive to share the burden through price adjustments. Contracts that lock in FOB Canadian prices without duty change provisions leave the importer holding the full cost increase.

Key Takeaways

Three presidential proclamations signed July 20, 2026 under 19 U.S.C. § 1338 impose a 50% additional ad valorem duty on covered Canadian imports, effective 12:01 a.m. ET on August 19, 2026.
This is the first invocation of Section 338 to impose tariffs in roughly 80 years. The statute has never been successfully challenged in modern court. No stay is in effect as of August 1, 2026.
USMCA origination provides no relief. Unlike the now-vacated IEEPA tariffs on Canada, Section 338 applies to USMCA-qualifying goods.
The three proclamations target three Canadian practices: provincial restrictions on US alcohol, a dairy TRQ allocation that advantages EU producers over US producers, and Canada's surtax on US-made cars.
The motor vehicles proclamation is the broadest. Its 439 tariff lines don't cover actual vehicles (those are excluded as Section 232 goods) but sweep in cement, plywood, furniture, machinery, clothing, and a range of consumer goods across multiple HTS chapters.
Excluded categories: energy products, potash, fish, critical minerals, Section 232 goods (steel, aluminum, copper, automobiles, auto parts), and WTO civil aircraft products. There's no exclusion request process.
The 50% duty stacks on the base MFN rate, on the Section 301 forced labor tariff (10% for Canada, effective July 24), and on any applicable AD/CVD cash deposit rates.

Confirming whether your Canadian-origin goods are within the Section 338 proclamation scope starts with the correct 10-digit HTS code. TariffClassify classifies your product and shows the full duty stack including Section 338, Section 301, and all other overlays in a single view. Classify your first product free.