Mexico Customs Reform: Stricter Valuation Rules Threaten Border Delays

Mexican President Claudia Sheinbaum has introduced a significant overhaul of the country's Customs Law that would dramatically expand customs authorities' power to scrutinize and seize cross-border shipments suspected of undervaluation. The proposal, submitted to Congress in September 2026, eliminates the existing 50% undervaluation threshold for precautionary seizures and lowers the infraction threshold from 50% to 20% for goods in deferred-duty regimes. This legislative push aims to protect domestic manufacturers and recoup lost import duties but threatens to create substantial operational friction for cross-border supply chains. The timing and scope of this reform creates a critical intersection of risk for companies operating the US-Mexico trade corridor.

6 million escape precautionary seizure under the existing 50% threshold. The proposed changes would expose significantly more shipments to documentation challenges, cargo detention, and valuation disputes during transit. Automotive manufacturers are particularly concerned—industry association AMIA warns that the elimination of the 50% threshold could disrupt just-in-time operations if components are seized while valuation disputes are resolved. Bonded warehouses have flagged capacity and congestion risks if precautionary seizures spike.

For supply chain professionals, this reform necessitates immediate action on three fronts: strengthen customs valuation documentation for all cross-border transactions (especially related-party sales, royalties, and transfer pricing adjustments); reassess safety stock and buffer inventory strategies for critical components sourced from Mexico; and engage trade counsel to model compliance costs under the new regime. The legislative vote is expected imminently, and the amendments would take effect the day after publication in Mexico's official registry.