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Two containers of the same British cheese can reach Manzanillo on the same day and clear at two different rates. One enters free of the Impuesto General de Importación (IGI, Mexico's general import duty). The other pays the full rate set in the Ley de los Impuestos Generales de Importación y de Exportación (LIGIE), a rate that rose at the start of 2026. Same product, same supplier, same Treaty. What separates the two outcomes is documentation that had to exist before either container moved.
As of June 22, 2026, the United Kingdom is a party to the Tratado Integral y Progresista de Asociación Transpacífico (TIPAT, known internationally as the CPTPP) for Mexico. UK-origin goods can now enter under the Treaty's preferential rates. Whether a given shipment captures that preference or reverts to the full tariff is a decision made upstream, in the file, not a status the border confers on arrival.
Zero or full rate: the two cost paths on one product
Start with the number, because the number is what moved. For most UK-origin goods, the TIPAT rate is now exemption from the IGI. Not every line reaches zero on day one: the Treaty groups goods into baskets that phase down to zero on fixed January 1 dates, with the final tranches landing in years such as 2027, 2029, 2030, and 2033 under the elimination schedule of Annex 2-D. For the bulk of goods, though, the preferential path is already duty-free as of today.
The other path is the fallback, and it is heavier than it was a year ago. The December 29, 2025 reform to the LIGIE raised Mexico's general import duty across a wide range of fractions, effective January 1, 2026. A UK-origin good that fails to secure its preference does not pay a small premium. It pays the current general rate on its full customs value. For the sensitive goods we come to below, the acuerdo is explicit: where the requirement is not met, the rate to apply is the one in Article 1 of the LIGIE, "sin reducción alguna" (with no reduction whatsoever).
The gap between those two paths, on the same shipment, is the entire reason this change is worth your attention. Preference is not the default. It is the better of two outcomes, and you select it with paperwork.
What changed on June 22, and why it lands now
The United Kingdom's Protocol of Accession to the TIPAT entered into force for Mexico on June 22, 2026. Mexico notified the Treaty's depositary that it had completed its internal legal procedures on April 23, 2026, and under the Protocol accession takes effect sixty days after that notification. Sixty days from April 23 is June 22, which is why the Secretaría de Economía published two acuerdos in the Diario Oficial de la Federación (DOF) that day, both effective on publication.
The first acuerdo inserts the United Kingdom into the decree that sets the preferential IGI rate for TIPAT-origin goods (originally published September 5, 2022). The second adds the United Kingdom to the administration of import quotas (cupos) for a defined list of sensitive goods: dairy (milk, cream, milk powder, evaporated and condensed milk, butter, cheese, and dairy preparations) and palm oil.
Until yesterday, Mexico and the United Kingdom traded under the bilateral Acuerdo de Continuidad Comercial that carried the relationship through the post-Brexit period. From today, the preferential framework for these goods is the Treaty, which means a different rules-of-origin model and a different certification path. There is no transition window to prepare. The rate is live now.
Which path your goods take: the decision framework
For an importer of British goods, three questions decide which rate shows up on the pedimento.
The first question is what kind of good you are moving. Most UK-origin goods sit in the general preferential treatment and are exempt, subject to the staging calendar. A specific set, the dairy and palm oil lines in Apéndice I of the rate acuerdo, is quota-bound. The handling is different, and the difference is the whole question.
The second question is origin. A good shipped from the United Kingdom is not automatically an originating good. It must qualify under Chapter 3 of the Treaty (Reglas de Origen y Procedimientos Relacionados con el Origen), against the product-specific rule for its classification. The certification of origin can be completed by the exporter, the producer, or the importer (Article 3.20), but the certification and the records behind it have to exist and hold up under a later verification. Origin is a claim you prove, not a label you assume.
The third question applies only to the quota-bound goods, and it is where most operations will slip. For the dairy lines, the exemption applies only when the importer holds a certificado de cupo issued by the Secretaría de Economía. If that certificate is not in hand, the rate that applies is the LIGIE rate, with no reduction. A cupo confirmed after the goods arrive does not retroactively repair a clearance that already happened at the full rate.
In our work across the corridor, the pattern is consistent. Across more than 190,000 customs operations a year at 39+ ports on both sides of the border, the preferences that hold up are the ones built upstream, before the cargo moves. The failures are almost never failures of eligibility. They are failures of timing: the good qualified, but the cupo certificate or the origin file was not ready when the shipment was.
One thing the preference does not touch: it changes the duty, not the rest of the file. The acuerdos restate that preferential treatment does not waive regulaciones y restricciones no arancelarias, applicable Normas Oficiales Mexicanas (NOMs), or the ordinary customs clearance process. A zero rate on a product that still needs a NOM certificate is not a faster clearance.
The moves that put you on the preferential path
Four moves decide which of the two rates your shipment meets.
→ Classify each UK-origin good against the two lists. Confirm whether the fraction sits in general preferential treatment or in the quota-bound Apéndice I (dairy, palm oil, and certain sugar). This single check tells you whether a cupo is in your critical path.
→ For any quota-bound good, secure the certificado de cupo from the Secretaría de Economía before the shipment departs. Treat it as a gating document, not a formality to chase later.
→ Build the origin file before the cargo moves. Decide who certifies, obtain the certification against the product-specific rule, and assemble the supporting records so an originating claim survives a verification months after the fact.
→ Model both outcomes. Run the landed cost at the preferential rate and at the full LIGIE fallback. Knowing the exposure if origin or cupo fails is what turns the preference from a hope into a planned position.
The United Kingdom joining the TIPAT is a real opening for importers: preferential access to one of the world's largest economies under modern rules. But the opening is conditional. On the same shipment, the difference between zero duty and a full, recently raised tariff comes down to two documents and the discipline to have them ready before the truck rolls. The border does not grant the preference. The file does.
Talk to a Joffroy expert about origin qualification and cupo certificates for your UK-origin imports.
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