Mexico’s customs law reform: Lower seizure thresholds and higher penalties for hydrocarbon-related customs violations

On October 23, 2026, a decree amending Mexico's Customs Law (Ley Aduanera) as part of the 2027 Economic Package was published in the Official Gazette of the Federation (Diario Oficial de la Federación). The amendments, which will take effect on January 1, 2027, introduce stricter customs valuation requirements, expand the circumstances under which customs authorities may seize undervalued goods, and significantly increase penalties for customs violations involving hydrocarbons and petroleum products.

This alert outlines the principal amendments and their implications for import and export operations, examines their relationship to other recent developments in Mexico's customs regulatory framework, and provides recommended next steps for businesses preparing for the new requirements.

What's changing

Expanded seizure powers for undervaluation below the previous 50% threshold

Under the current framework, Mexico's National Customs Agency (Agencia Nacional de Aduanas de México, or "ANAM") may seize imported goods when their declared value is 50% or more below the value of identical or similar merchandise; this seizure power does not apply to goods subject to official estimated prices where the importer has posted the corresponding guarantee under Article 86-A of the Customs Law. Neither limitation survives the reform: ANAM will be able to initiate seizure proceedings regardless of the size of the undervaluation, including for goods that would previously have been protected by that guarantee.

In addition, customs authorities will be required to initiate an audit whenever the declared value of imported goods is below the relevant reference value. For goods imported under customs regimes that defer the payment of duties, including temporary importation, the threshold for presuming a customs violation will be reduced from 50% to 20%.

This change closes the gap left by the previous fixed 50% threshold, under which moderate undervaluation went unchallenged. The sectors most exposed are likely those historically subject to official reference prices, including footwear, textiles and apparel. As a result, even relatively minor discrepancies in declared customs values may lead to the seizure of imported goods and the vehicles transporting them, as well as the initiation of an audit. Importers should therefore ensure that comprehensive, accurate and up-to-date valuation documentation (including commercial invoices, pricing support, applicable shipping terms and records substantiating the declared customs value) is readily available at the time of importation, rather than assembled only in response to a subsequent customs review.

New 20% threshold for the release of seized goods

Under the amended framework, where imported goods are seized and are not subject to official reference prices, importers may request the substitution of the seizure with a guarantee to secure the release of the merchandise. The applicable requirements will depend on the extent of the discrepancy between the declared customs value and the relevant reference value:

• Discrepancies below 20%: Importers will have 10 business days to request the release of the seized goods by providing either a cash deposit or a guarantee through a customs guarantee account, covering the applicable duties and compensatory quotas.
• Discrepancies of 20% or more: The release of seized goods will require a cash deposit, as the option to provide a guarantee through a customs guarantee account will no longer be available.

Where importers demonstrate lawful possession of the merchandise, establish that the grounds for seizure were unfounded, or substantiate the accuracy of the declared customs value, customs authorities must release the seized goods and any associated deposit or guarantee immediately, without imposing penalties. In all other cases, the authorities will have four months to issue a final determination, failing which the proceedings will lapse.

The new 20% threshold has important implications for importers' cash-flow management. While discrepancies below this threshold allow greater flexibility in the type of guarantee provided, discrepancies of 20% or more may require importers to provide a cash deposit covering the applicable duties and compensatory quotas until the proceedings are resolved. Importers of goods historically subject to official reference prices, including footwear, textiles and apparel, should also review their existing customs guarantee arrangements in light of these changes.

Increased penalties for customs violations involving hydrocarbons and petroleum products

The reform significantly increases the penalties applicable to inaccurate, incomplete or false customs documentation involving hydrocarbons and petroleum products. Such violations will now be subject to fines ranging from 50% to 100% of the commercial value of the merchandise, representing a substantial increase compared with the fixed monetary penalties that continue to apply to similar violations involving other categories of goods.

The heightened penalties increase compliance risks for businesses engaged in the importation, exportation, storage, transportation or blending of hydrocarbons and petroleum products.
Companies operating in these sectors should therefore review their customs declaration procedures, supporting documentation and internal compliance controls to mitigate the risk of violations and the potentially significant financial consequences associated with inaccurate or incomplete filings.

Broader developments in Mexico's customs enforcement framework

The Customs Law reform forms part of a broader effort to strengthen customs enforcement in Mexico. Several related regulatory developments introduced during 2026 will also influence the implementation of the new requirements.

Phased implementation of the electronic value declaration

The Electronic Value Declaration (Manifestación de Valor Electrónica or "MVE") requires importers to electronically declare and substantiate the customs value of imported goods through Mexico's Single Window for Foreign Trade ("VUCEM"), replacing the previous paper-based process. Following several postponements, mandatory implementation will occur in stages according to the applicable customs regime:

• November 1, 2026: Manufacturing, processing or repair in a bonded facility.
• November 15, 2026: Strategic bonded facilities.
• December 1, 2026: Transit of goods.
• December 15, 2026: Bonded warehouse.
• January 1, 2027: Temporary importation.
• January 15, 2027: Definitive importation.

The MVE will serve as a key mechanism for substantiating declared customs values under the stricter valuation requirements introduced by the reform. As several implementation dates coincide with the January 1, 2027 effective date of the Customs Law amendments, importers will face overlapping compliance obligations. Late or incomplete filings may result in penalties, valuation adjustments or seizure of goods, independently of any undervaluation findings.

Repeal of reference pricing for textiles, apparel and footwear

Effective September 15, 2026, Mexican authorities repealed the reference pricing mechanism covering 757 tariff classifications for textiles, apparel and footwear, together with the associated import permit requirement. Guidance issued on October 5, 2026 clarified that consolidated customs declarations remain subject to the rules in effect on the date of the first shipment, even if the declaration is completed after the repeal.

With the elimination of reference pricing, importers in these sectors, which previously relied on related customs guarantee accounts, will face greater reliance on general customs valuation and audit procedures, including those strengthened under the reform.

Related trade remedy developments

Mexico has also pursued separate antidumping proceedings, which, like the Customs Law reform, address concerns regarding the underpricing of imported merchandise.

These proceedings are conducted under a separate legal framework from customs valuation enforcement.

Additional amendments

• Seizure procedures: The reform consolidates the procedures for resolving seizure cases into a single provision, linking the conditions for releasing seized goods and the four-month deadline for issuing a final determination to the new undervaluation rules.
• Implementing provisions: By December 31, 2026, customs authorities must publish the list of goods subject to the new seizure rules and the applicable valuation thresholds for other goods. These implementing provisions will define the scope of the new requirements for specific products.

Recommended next steps

1. Strengthen customs valuation documentation: Ensure that commercial invoices, shipping terms, related-party pricing support and records substantiating declared customs values are accurate and up to date before January 1, 2027. Even minor discrepancies may trigger customs enforcement measures.
2. Review customs guarantee arrangements: Assess existing customs guarantee accounts against the new 20% threshold to anticipate potential cash-flow implications.
3. Assess compliance controls for hydrocarbons and petroleum products: Review customs declarations and supporting documentation in light of the significantly increased penalties for inaccurate, incomplete or false filings.
4. Monitor implementing regulations: Follow the publication of ANAM's implementing provisions, expected by December 31, 2026, which will define the goods subject to the new seizure rules and the applicable valuation thresholds.
5. Prepare for MVE implementation: Review import operations against the phased implementation schedule, running from November 2026 through January 15, 2027, and ensure readiness to comply with the new electronic valuation requirements.
6. Reassess procedures for textiles, apparel and footwear: Review consolidated shipments affected by the September 15, 2026 repeal of reference pricing and update customs guarantee arrangements to reflect the revised requirements.

For further information regarding this alert or international trade and customs matters in Mexico, please contact our Mexico City Trade Team.

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