The 10% Section 301 Duty Is Live: Only Goods Actually Entered Under USMCA Escape It

At 12:01 a.m. eastern time on July 24, 2026, an additional 10% duty took effect on products of Mexico entering the United States, under the final Section 301 action the U.S. Trade Representative announced one day earlier. The exemption that matters most to Mexico-sourced supply chains is written into the action itself: goods of Mexico entered free of duty under the USMCA do not pay it. That single clause now carries 10% of the customs value of every shipment. And it turns on a distinction many importers have never had to price: not whether goods are eligible to qualify under the agreement, but whether they actually enter under it, with a valid preference claim at entry, a defensible origin qualification behind the claim, and the correct tariff classification behind the qualification.

What took effect on July 24

The action is the final determination in the Section 301 investigations USTR opened into 60 economies over their failure to impose and effectively enforce prohibitions on the importation of goods produced with forced labor (Federal Register notice of action, Dockets USTR-2026-0265 and USTR-2026-0266). The remedy is an additional ad valorem duty on all products of the investigated economies, subject to exemptions set out in two annexes.

Two base rates apply. Economies that maintain a forced labor import prohibition, have committed to one through an Agreement on Reciprocal Trade, or operate a partial regime that prevents the importation of certain forced labor goods pay 10%. Mexico sits in this group, alongside Canada, the United Kingdom, India and thirteen others. Most other investigated economies pay 12.5%, and a defined set of products from the European Union, Japan, Korea, Taiwan and Switzerland pays 10% or 12.5% net of the most favored nation rate.

These duties stack on top of whatever the entry already pays: the MFN rate, any antidumping or countervailing duties, and any applicable Section 232 treatment. They also arrived the same day the temporary Section 122 global surcharge lapsed, which means the additional-duty floor on non-USMCA Mexican goods did not fall to zero on July 24. It changed legal basis and stayed at 10%.

The exemptions are where the operational work lives. U.S. Note 52 to the tariff schedule excludes, among others, goods covered by enumerated Section 232 programs, most Chapter 98 entries, donations intended to relieve human suffering, informational materials, and, decisive for this corridor, goods of Canada and Mexico entered free of duty under the USMCA. CBP issued its filing guidance the evening before the duties took effect (CSMS #69326983).

The dates that matter, and the four days still open

The timeline compressed fast. USTR initiated the 60 investigations on March 12, 2026. On June 2 it published its findings and the proposed duties, taking written comments through July 6. Public hearings ran July 7 through 9, with over 1,600 written comments and more than 100 witnesses on the record. The notice of final action landed July 23, and the duties took effect at 12:01 a.m. eastern time on July 24. From proposal to collection: seven weeks.

One window remains open. Goods loaded onto a vessel at the port of loading and in transit on their final mode of transit before 12:01 a.m. eastern time on July 24, and entered for consumption or withdrawn from warehouse for consumption before 12:01 a.m. eastern time on July 28, are not subject to the additional duty.

Quick check: for cargo moving this week, two facts decide each shipment: the date it was loaded on its final mode of transit (before July 24) and the projected date of entry or withdrawal (before July 28). Confirm both, shipment by shipment, today. After July 28 there is no transition margin left.

The trap: eligible is not entered

On paper, most Mexico-sourced manufacturing supply chains look protected. Regional content runs high, the corridor was built around the agreement, and the goods "are USMCA." In practice, the exemption does not attach to goods that could qualify. It attaches to goods entered free of duty under the agreement. The difference is procedural, evidentiary, and now worth 10% of customs value on every entry.

Three failure modes will account for most of the surprises.

The first is the unclaimed entry. For years, when the MFN rate on a product was already zero, many importers skipped the USMCA claim: same duty outcome, less paperwork. That math inverted on July 24. A duty-free good entered without a preference claim is not entered under the USMCA, and the additional 10% applies. The claim itself, properly made at entry and supported by a certification of origin, is now the shield.

The second is the habitual certification. A certification of origin is a legal declaration that a qualification analysis exists: that someone determined the good meets its product-specific rule of origin, through tariff shift, regional value content, or both, and can produce the records behind that determination. Certifications renewed every January out of routine, without re-running the analysis against current sourcing and current bills of materials, are exactly the files that do not survive verification.

The third is classification. Product-specific rules of origin are keyed to tariff classification: the HTS code of the finished good determines which rule applies, and the codes of its inputs determine whether the required tariff shift occurred. A wrong classification used to cost, at worst, a duty-rate correction. It can now invalidate the origin analysis itself, because the qualification was run against the wrong rule. When the claim fails, the entry reverts to dutiable status and picks up the additional 10%. And under the reasonable care standard, the party that answers for the claim is the importer of record, not the broker and not the supplier.

What to do in the next 30 days

Map your entries by claim status, not by product. Split your last 90 days of entries from Mexico into two groups: those that carried a USMCA preference claim and those that cleared at MFN rates without one. Every entry in the second group is now paying, or is about to pay, 10% that a valid claim may eliminate. That list is your priority queue.

Re-validate certifications against evidence, not habit. For each certification of origin on file, confirm it is current, complete in its required data elements, and backed by a qualification analysis that you or the certifier can actually produce: the regional value content calculation or the tariff-shift determination, tied to a live bill of materials. Where the analysis does not exist, commission it before continuing to rely on the certification.

Audit classification where the money is. Rank your fracciones by customs value and verify the classification at the top of the list first. Those codes now carry two consequences at once: the duty rate and the rule of origin your exemption depends on.

Put a number on the residual exposure. For goods that cannot qualify, or whose qualification is genuinely uncertain, the cost is now explicit: 10% of customs value per shipment, on top of existing duties. That number tells you whether the answer is a qualification project, a sourcing change, or absorbing the duty deliberately.

Across more than 190,000 customs operations a year at 39+ ports, the pattern this week is consistent: the operations moving calmly are the ones whose origin files were already built as evidence, reconciled and retrievable, and the scramble is concentrated where certification had become an annual formality.

The claim is now the tariff position

What changed on July 24 is not the paperwork. It is the price of the paperwork being wrong. The USMCA claim used to be a preference; for products of Mexico under this action, it is the tariff position, and it has to be earned entry by entry: claimed at entry, classified correctly, and provable on demand. Importers who treat this week as a one-time deadline will close the gap once. The ones who treat it as the new baseline will keep the 10% off their landed cost for as long as the action runs.

Talk to a Joffroy expert about a USMCA claim and origin-file review for your Mexico entries before your next shipment crosses.

TRADE. UNDER CONTROL.