Mexico Steel & Aluminum Tariffs (15%–50%): IMMEX Annex II, Automatic Notices & PROSEC / Regla Octava

Between August 2023 and April 2024, with enforcement tightening further through 2025 and 2026 in coordination with US Section 232 trade enforcement, the Mexican Federal Government enacted sweeping temporary tariff decrees modifying the TIGIE (General Import and Export Tax Law). These decrees raised Mexican General Import Duties (IGI) to 15%, 20%, 25%, 35%, and up to 50% across more than 540 tariff fractions, hitting Chapters 72 and 73 (Iron and Steel) and Chapter 76 (Aluminum) hardest.

For US metal stampers, appliance manufacturers, HVAC producers, automotive suppliers, and electrical enclosure plants operating in Mexico under IMMEX, these tariff decrees created a triple compliance wall at the border:

1. 15%–50% Mexican Import Duties (IGI) triggered via USMCA Article 2.5,
2. IMMEX Annex II (“Sensitive Goods”) restrictions blocking temporary importation (Clave IN) for unauthorized importers, and
3. Automatic Steel Import Notices (Avisos Automáticos Siderúrgicos: Clave C6) requiring verified Mill Test Certificates (Certificados de Molino) showing where the steel was melted and poured.

Here is the operational blueprint to legally eliminate the 15%–50% tariff exposure and prevent border seizures on steel and aluminum shipments.

1. Why IMMEX Plants Get Hit by 15%–50% Steel & Aluminum Tariffs

When US companies first encounter a 25% or 35% Mexican steel tariff bill on a temporary import pedimento (Clave IN), their immediate reaction is: “Why are we paying Mexican import duty on a temporary IMMEX import that is 100% exported back to the United States?”

The answer lies in USMCA Article 2.5 (Treatment of Duties on Non-Originating Goods / Duty Deferral) and Article 63-A of the Mexican Customs Law:

• If your Mexican plant imports steel coil, electrical steel, stainless bar, or aluminum extrusions that do not qualify as USMCA-originating (either because they were produced in Japan, South Korea, Taiwan, Germany, Brazil, or China, or because they were processed in a US service center from foreign slab/substrate without satisfying the applicable Annex 4-B tariff-shift rule),
• And your Mexican plant stamps, fabricates, or assembles that metal into a finished product exported to the United States or Canada,
• Mexico’s IMMEX duty exemption is revoked for the non-originating metal. You must pay the Mexican General Import Tax (IGI), now 15% to 50% MFN, reduced only by the US import duty paid upon entry into the US (which is 0% if the finished assembly qualifies under USMCA).

Even worse: if a US service center ships Korean or European steel from a Texas warehouse to your Monterrey or Querétaro plant without a valid USMCA Certificate of Origin (because the steel only underwent slitting or pickling in Texas, which does not confer USMCA origin), Mexican customs treats that shipment from Texas as non-originating foreign steel subject to the full 15%–50% tariff.

2. How to Legally Reduce the 15%–50% Tariff to 0%: PROSEC & Regla Octava

To eliminate the 15%–50% Mexican IGI on non-originating steel and aluminum without violating USMCA Article 2.5, IMMEX manufacturers rely on two domestic Mexican tariff-reduction mechanisms built directly into the TIGIE and Sectoral Decrees:

How to Apply for a Steel or Aluminum Regla Octava (98.02) Permit

Because Mexican domestic steel producers (CANACERO) actively monitor Regla Octava applications, approval via VUCEM requires rigorous technical documentation:

1. Active PROSEC (+ Active IMMEX for temporary imports) in the corresponding manufacturing sector (Sector I, II, XV, XIX, etc.), with current Annual Operation Reports (RAOCE) filed on time.
2. Technical Justification by Criteria:
   • Unavailability / Insufficient Domestic Production (Inexistencia o Insuficiencia de Producción Nacional): Technical specifications (ASTM / JIS / DIN grade, tensile strength, gauge tolerance, coating weight, magnetic core loss for electrical steel) proving that Mexican mills either do not manufacture the specification or cannot supply the required volume/lead time.
   • Pre-Export / Customer Technical Mandate (Bienes requeridos en etapa previa o por especificación técnica): OEM engineering prints or PPAP approvals mandating a specific qualified mill source.
3. Volume Reconciliation: Every Regla Octava permit authorizes a strictly capped volume (in Kilograms or Metric Tons) and expiration window. Your customs broker’s pedimento discharges cannot exceed the authorized permit balance by a single kilogram.

3. IMMEX Annex II (“Sensitive Goods”) Authorization for Steel & Aluminum

Even if you are willing to pay the tariff or hold a PROSEC registration, you cannot legally import most Chapter 72, 73, and 76 steel and aluminum tariff codes on a temporary IMMEX pedimento (Clave IN) unless your IMMEX program is authorized for Annex II Sensitive Goods (Anexo II del Decreto IMMEX).

Mexico places steel and aluminum in Annex II (Apartado B / C) to prevent triangulation and illegal diversion into the domestic market. You have two paths to clear the Annex II barrier:

1. Certified Companies (Certificación IVA e IEPS under RGCE Rule 7.1.2):
   • Companies holding an active IVA & IEPS Certification (Rubro A, AA, or AAA) that have specifically applied for and received Sensitive Goods Authorization (Autorización para importar mercancías sensibles del Anexo II) from SAT/AGACE under Rule 7.1.2 (demonstrating physical production infrastructure, SCCCyG compliance, and validated suppliers).
2. Ministry of Economy Annex II Expansion (Ampliación de Mercancías Sensibles):
   • For non-certified IMMEX companies (or certified companies requiring specific fractions through Secretaría de Economía), filing a formal Annex II Expansion Request backed by a CPA report (Reporte de Contador Público Registrado) verifying installed stamping/machining capacity, headcount, and historical export ratios, which grants a volume-capped quota valid for 4 to 12 months.

4. The Automatic Steel Import Notice (Clave C6) & Mill Test Certificates

For more than 100 tariff fractions in Chapters 72 and 73, every shipment, whether definitive (A1) or temporary (IN), and regardless of whether it comes from the US, Canada, or Asia, requires an Automatic Import Notice for Steel Products (Aviso Automático de Importación de Productos Siderúrgicos, Appendix 9 Clave C6) approved via VUCEM before crossing the border.

The 3 Golden Rules of Clave C6 Steel Notices & Mill Certificates (MTCs)

1. Country of Melt and Pour (País de Fundido y Colado) vs. Country of Origin (País de Origen):
   • Every VUCEM Aviso Automático Siderúrgico requires declaring three distinct geographic fields:
     • País donde se fundió y coló el acero (Country where the raw liquid steel was originally melted in the furnace and poured into primary form: slab, billet, or bloom),
     • País de origen (Country where the steel underwent its last substantial transformation into the imported tariff code, such as cold rolling or galvanizing), and
     • País de procedencia (Country from which the steel was shipped to Mexico, e.g., a service center in Houston, Texas).
2. Mandatory Mill Test Certificate (Certificado de Molino) vs. Quality Certificate (Certificado de Calidad) by Tariff Heading:
   • Under official SNICE / Ministry of Economy rules (Annex 2.2.1 & 2.2.2), the required certificate depends strictly on the 4-digit tariff heading (partida):
     • Mill Test Certificate (Certificado de Molino) — Mandatory for headings 7206 to 7216, 7218 to 7228, and 7304 (ingots, flat-rolled coils/sheets, bars, rods, angles, stainless steel, and seamless pipes/tubes). Must be issued directly by the primary steel mill that melted and poured the heat (colada).
     • Quality Certificate (Certificado de Calidad) — Mandatory for headings 7202, 7217, 7229, 7301, 7302, and 7305 to 7317 (ferroalloys, drawn wire, sheet piling, welded tubes, structures, stranded wire/cables, chains, and nails/tacks; note that 7318 screws/bolts are generally excluded from the C6 notice). Issued by the manufacturer of the transformed steel article (or accompanied by the underlying Mill Test Certificate).
   • A commercial invoice or packing list issued by a US steel distributor or service center is rejected by the Ministry of Economy unless accompanied by the formal Mill Test Certificate or Manufacturer Quality Certificate containing chemical composition, heat/lot number, and norm compliance.
3. 5-Day VUCEM Processing Lead Time & Annual RIPS Registry (Esquema B):
   • The Ministry of Economy takes up to 5 business days to approve or reject a shipment-by-shipment Aviso Automático Siderúrgico. Never dispatch a flatbed truck to Laredo or Colombia Bridge before the C6 permit number is issued and verified against the exact invoice weight, tariff fraction (10 digits), and mill country.
   • For frequent steel importers, evaluate registering in the Steel Importers Registry (RIPS — Registro de Importadores de Productos Siderúrgicos, Esquema B), which grants an annual registration per 10-digit tariff fraction authorizing one or multiple automatic notices without waiting 5 business days per shipment, subject to mandatory quarterly import reports.