Mexico Manufacturing 2026-11-04 Editorial Team at ammex.org.mx

Contract Manufacturing vs. Submaquila (Article 21 IMMEX) in Mexico: Complete Legal & Customs Guide

When US supply chain executives and Mexican plant managers outsource production or specialized industrial processes in Mexico, such as CNC machining, metal stamping, plastic injection molding, electroplating, heat treating, PCBA surface-mount assembly, or kitting, they frequently evaluate the vendor solely on unit price, lead time, and ISO/IATF quality certificates.

In Mexico, however, how the raw materials and tooling legally enter, move between facilities, and exit the country is just as critical as the vendor’s quality system. Moving temporarily imported IMMEX materials to a Mexican supplier or subcontractor under the wrong customs figure can trigger 16% non-recoverable VAT, block your Anexo 24 and Anexo 30/31 (SCCCyG) discharges, or expose your inventory and molds to a PAMA seizure.

1. The 5 Legal Manufacturing & Outsourcing Models in Mexico

Before issuing an RFQ or shipping a single pallet of raw materials or tooling to a Mexican vendor, identify which of these five legal structures governs the relationship:

Manufacturing Model	Who Owns the Raw Materials & WIP?	Vendor’s Required Customs Status	How Materials Enter & Exit the Vendor’s Plant	How the Vendor Invoices You
*1. Turnkey Contract Manufacturing (Buy-Sell CM)*	The Mexican CM buys raw materials on its own account (or imports them under its own IMMEX).	IMMEX Industrial Modality (Art. 3-I Decree) or Definitive Importer (`A1`).	CM imports directly (`IN`/`A1`) and exports finished goods to the US (`RT`/`A1`) or transfers via `V1` to your Mexican plant.	Invoices 100% of the finished product unit price at 0% VAT (for direct export or `V1` transfer).
*2. Consignment Contract Maquila (Foreign Principal -> Mexican CM)*	The US Customer retains legal title to all raw materials and tooling on consignment.	IMMEX Industrial or Services Modality + IVA/IEPS Certification.	US Customer ships consigned inputs from the US; the Mexican CM acts as Importer of Record (`IN`/`AF`), tracks your BOM in its Anexo 24, and returns (`RT`) to the US.	Invoices only the processing/assembly service fee at 0% VAT (Art. 29, Sec. IV, b) LIVA).
*3. Submaquila / Submanufactura (Mexican IMMEX Plant -> Local Process Shop)*	Your Mexican IMMEX Plant (or your US parent) retains legal title and customs custody.	Vendor must be *registered as a Submanufacturero* under Art. 21 IMMEX Decree** in your VUCEM profile (vendor does NOT need its own IMMEX!).	Moves physically from your Mexican plant to the vendor and back via CFDI de Traslado + Carta Porte 3.1 + Monthly Rule 4.3.7 SAT Notice (Ficha 71/LA) (No pedimento filed!).	Local vendor invoices a domestic processing service (+16% Mexican VAT) to your Mexican entity.
*4. Virtual Supply Chain Transfer (IMMEX Tier-2 -> IMMEX Tier-1)*	Title and customs liability transfer from the Tier-2 supplier to the Tier-1 buyer.	Both parties MUST hold active IMMEX programs.	Delivered inside Mexico accompanied by mirror Virtual Pedimentos (`Clave V1`: Rule 4.3.21).	Invoices the component sale at 0% VAT (if billed by a foreign entity or under applicable Art. 29 LIVA rules).
*5. IMMEX Services Modality (Kitting, Rework, Testing, Sorting)*	Foreign customer or another IMMEX plant owns the goods.	IMMEX Services Modality (Art. 3-II Decree & Annex 3.2.2 SE Rules).	Enters via `IN` or `V1` strictly for non-transformative services (inspection, repair, re-packaging, labeling) and exits via `RT` or `V1`.	Invoices the service fee.

2. Submaquila (Article 21 IMMEX) vs. Virtual Transfer (`V1`): Choosing the Right Domestic Mechanism

One of the most frequent operational questions for a US-owned plant already operating in Mexico is: “We imported aluminum castings or steel coils temporarily on an IN pedimento, and now we need to send them to an outside shop in Monterrey for heat-treating, anodizing, or CNC machining before they come back to our plant for final assembly. Do we use a V1 Virtual Pedimento or an Article 21 Submaquila?”

Look at the exact legal and operational difference between the two routes:

Route A: Article 21 Submanufactura / Submaquila (RGCE Rule 4.3.7 & Ficha 71/LA)

This is the statutory mechanism designed specifically for outsourcing a partial industrial process when the material is coming back to your plant (or when the vendor is a specialized local Mexican shop that does not have its own IMMEX program):

VUCEM Prior Registration (Article 21 IMMEX Decree):
- Before sending a single piece to the vendor, your compliance team logs into VUCEM and registers the subcontractor’s RFC and exact plant address under your IMMEX program as an authorized Submanufacturero de Exportación.
- To be approved by the Ministry of Economy, the subcontractor must have an active RFC, a positive 32-D tax compliance opinion, and a verified (localizado) tax domicile, and cannot have uncredited directors/shareholders on SAT blacklists.
Zero Pedimento Cost: Moves on CFDI de Traslado + Carta Porte 3.1:
- Because there is no change of customs regime and no transfer of IMMEX ownership, you do not pay a customs broker to file V1 pedimentos.
- Instead, when your truck (or third-party carrier) leaves your plant for the subcontractor’s shop, it carries a CFDI de Traslado with the Carta Porte 3.1 supplement and a Submaquila Remission Memo referencing your IMMEX authorization and the VUCEM submanufacturer registration number (Article 146 Customs Law & Article 21 IMMEX Decree; note that if you also loan temporary machinery or tooling AF to the submanufacturer, that equipment transfer is covered by RGCE Rule 4.3.6).
Inventory Remains on YOUR Anexo 24 and YOUR Anexo 30/31 (SCCCyG):
- While the parts are sitting at the subcontractor’s facility being machined or plated, they remain 100% part of your open IN balance in Anexo 24 and your SCCCyG credit ledger. Under Article 21 of the IMMEX Decree, the subcontractor is jointly and severally liable (responsable solidario) with you for the taxes on the goods in their custody.
Mandatory Monthly Notice to SAT Within the First 5 Days (RGCE Rule 4.3.7 & Ficha de Trámite 71/LA):
- Critical compliance rule: Within the first 5 days of every calendar month, your IMMEX company must transmit to SAT (via VUCEM) the Monthly Notice of Transfer of Merchandise for Submaquila (Aviso mensual de transferencias para realizar operaciones de submaquila) under RGCE Rule 4.3.7 and Ficha de Trámite 71/LA of Anexo 2, detailing every shipment sent to registered submanufacturers during the prior month. Failing to file those monthly notices invalidates the legal stay of the inventory outside your plant!

Route B: Virtual Transfer Pedimento (`Clave V1`: RGCE Rule 4.3.21)

Use a Virtual Pedimento (V1) instead of Submaquila when:

You are selling a component or sub-assembly to another IMMEX plant in Mexico and transferring permanent custody to them (the parts will not come back to your plant); or
You are buying a manufactured component from a Tier-2 supplier in Mexico that imported its own raw materials under its own IMMEX program and wants to discharge its Anexo 24/31 by transferring the customs liability to your IMMEX program.

3. 6-Point Customs Due Diligence Checklist Before Hiring a Mexican Contract Manufacturer

If your US company is contracting a Mexican supplier to manufacture products using your consigned materials or your consigned injection molds/test fixtures (Tooling), audit these six compliance controls before signing the manufacturing agreement:

Verify Active IMMEX, IVA/IEPS Certification (Rubro A/AA/AAA), and 32-D Status: Request copies of the supplier’s original IMMEX authorization, their latest May Annual Report (RAOCE) receipt, their active RECE IVA/IEPS Certification resolution, and this month’s positive 32-D tax opinion. If a supplier loses its IVA/IEPS Certification mid-contract, every consigned shipment you send them will suddenly require 16% cash VAT at the border!
Confirm VUCEM Domicile Registration for the Exact Building: Verify that the exact street address and building number where your materials and molds will sit are registered as an active plant/warehouse domicile in the supplier’s RFC and VUCEM IMMEX profile (Article 24 IMMEX Decree).
Segregation of Customer-Consigned Inventory in Anexo 24: Ask the supplier’s compliance manager to show you on screen how their Anexo 24 software segregates your consigned part numbers, your IN pedimentos, and your BOMs from their other customers so your materials are never cross-discharged on another customer’s exports.
Legal Protection for Your Consigned Molds, Dies & Test Equipment (AF + Bailment Contract):
- When the supplier imports your US-owned injection molds or end-of-line testers under their IMMEX (Clave AF), execute a formal, notarized Bilingual Bailment Agreement (Contrato de Comodato) that explicitly establishes your US company’s legal ownership, lists the exact Brand, Model, and Serial Number of every mold/fixture, and obligates the supplier to cooperate immediately in executing an RT return or V1 virtual transfer of your tooling upon contract termination (avoiding “tooling hostage” disputes).
Contractual Scrap & Waste Allowance (Mermas y Desperdicios: Article 109 LA): Define the maximum allowable scrap percentage in the contract and specify who pays the customs broker fees and duties to return (RT), destroy under SAT notice, or change the regime (F4) of rejected parts and runner scrap generated from your consigned materials.
Final Exit Reconciliation Clause: Make final commercial retainage payment contingent upon the supplier delivering 100% of closed RT/V1 return pedimentos and a zero-balance Anexo 24 reconciliation certificate for all consigned lots and tooling.

Frequently asked questions

What is the legal difference between Submaquila (Article 21 IMMEX) and a Virtual Pedimento Transfer (V1)?

Under Article 21 of the IMMEX Decree and RGCE Rules 4.3.6 and 4.3.7, Submanufactura (Submaquila) allows an IMMEX plant in Mexico to send its temporarily imported materials physically to a third-party Mexican shop (which does NOT even need its own IMMEX program) to perform a partial industrial process (such as heat treating, plating, CNC machining, or sub-assembly) and return the items back to the IMMEX plant WITHOUT filing a V1 pedimento. The original IMMEX company retains full customs and Anexo 24/31 liability for the inventory. By contrast, a Virtual Transfer (Clave V1 under Rule 4.3.21) occurs between two companies that BOTH hold active IMMEX programs and formally transfers the customs regime, Anexo 24 inventory balance, and SCCCyG VAT credit liability from the sender to the receiver.

Does a local Mexican machine shop or plating vendor need its own IMMEX program to perform Submaquila for our plant?

No. Under Article 21 of the IMMEX Decree, the third-party subcontractor (submanufacturero) can be a domestic Mexican company without an IMMEX program, provided that: 1) Your IMMEX company registers that vendor and its exact facility address in your IMMEX program via VUCEM prior to moving any goods; 2) The vendor holds a positive 32-D tax compliance opinion and active tax domicile; 3) All shipments to and from the vendor travel with a CFDI de Traslado + Carta Porte 3.1 supplement; and 4) Your company files the mandatory Monthly Submaquila Transfer Notice before SAT within the first 5 days of every month (RGCE Rule 4.3.7 and Ficha de Trámite 71/LA of Anexo 2).

What happens if we send temporary IMMEX inventory to a local Mexican vendor for processing without registering them under Article 21 or filing a V1?

That is a severe customs violation. Under Article 108 and Article 146 of the Mexican Customs Law and Article 27 of the IMMEX Decree, moving temporarily imported goods outside your authorized VUCEM registered domiciles to an unregistered third party is deemed illegal diversion of foreign merchandise, subjecting the goods in transit or at the vendor's shop to immediate PAMA seizure (Article 151, Section III), fines of 70%–100% of commercial value, and cancellation of your IMMEX program.

How should a US buyer choose between Turnkey Contract Manufacturing, Consignment Maquila, and Shelter in Mexico?

Turnkey Contract Manufacturing (Buy-Sell CM) is best when you want a Mexican supplier to use its own facility, workforce, and purchasing power to deliver a finished product at a fixed unit price without you owning inventory in Mexico. Consignment Toll Maquila is best when you supply proprietary components/tooling to a Mexican IMMEX supplier and pay only a processing fee per unit. Shelter (Albergue) is best when you want to control your own dedicated factory floor, engineering, and workforce in Mexico while outsourcing the Mexican legal entity, HR, and customs administration.

Can a registered Submanufacturero (Article 21) export the finished product directly to the United States on our behalf?

Under Article 21 of the IMMEX Decree and RGCE Rule 4.3.7, if the submanufacturer performs the final stage of production/packaging, the IMMEX holder can return the finished goods abroad directly from the registered submanufacturer's facility by declaring the corresponding submaquila identifiers and registered domicile on the export return pedimento (RT).

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