What Anexo 24 Really Is: The Inventory Control System That Keeps Your IMMEX Alive

Most IMMEX operators treat Anexo 24 as a filing chore, a report the customs broker produces and the authority files away. That reading costs cross-border manufacturers more than any other. Anexo 24 is the live, automated inventory control system that proves every temporarily imported input either left the country or was otherwise accounted for. While it holds, the duty deferral that makes your operation viable holds with it. When it breaks, the Servicio de Administración Tributaria (SAT, Mexico's tax authority) can treat your temporary imports as if they had stayed in Mexico for good, and the arithmetic that follows is large.

This is the explainer we wish every new IMMEX operator read before their first temporary import.

What Anexo 24 is

Anexo 24 is the annex to the Reglas Generales de Comercio Exterior (RGCE, Mexico's General Foreign Trade Rules) that defines the minimum content of the automated inventory control system every IMMEX company must run. Its legal spine sits in two places: Article 59, fracción I of the Ley Aduanera (Mexico's customs law), which obliges any importer to keep automated inventory control with a permanently current record of foreign-trade goods, and Article 24, fracción IX of the Decreto IMMEX, which ties that obligation directly to the program.

Operators usually call the system the SACI (Sistema Automatizado de Control de Inventarios). Companies holding the IVA/IEPS certification run a stricter version, the SECIIT, whose data is pulled electronically and cannot be edited by hand. Whatever the label, the SAT published the current specification as the Anexo 24 de las RGCE para 2026, so this is a live, versioned requirement.

One distinction saves operators a great deal of confusion: Anexo 24 and Anexo 31 are separate systems. Anexo 24 controls the physical inventory of temporarily imported goods. Anexo 31 controls the IVA and IEPS credit and guarantee accounts tied to certification. Each has its own failure modes, and each needs its own review.

How the Anexo 24 inventory control system works

The RGCE require the Anexo 24 system to do three things: comply fully with the Ley Aduanera, its regulation, and the RGCE on temporary-import inventory control; provide an instrument to verify returns and track goods still pending return; and generate the reports the authority can demand at any time.

To do that, the system carries a fixed set of catálogos (reference tables) and módulos (transactional modules). The catálogos identify the taxpayer, the materials used in production, the finished products, the suppliers and clients, any submanufacture or submaquila, and fixed assets. Each material and finished product carries its fracción arancelaria (tariff classification) and its unit of measure under the TIGIE (Mexico's tariff schedule). The módulos then record the movement: customs entries for temporary imports, the materials consumed, and the exits, meaning returns abroad, destructions, donations, régimen changes, or definitive imports.

The logic that matters is the descargo (discharge). A temporary import opens when the pedimento (Mexico's customs declaration) enters it into the system. It stays open, drawing down against your bill of materials as production runs, until it is discharged by a return, a transformation-and-export, a régimen change, or a definitive import with duties paid. Every open temporary import is a clock, because the Ley Aduanera sets permanence windows on how long goods may stay under the program before they must be discharged. An input left undischarged past its window is the single most common finding in an inventory audit.

To make the abstraction concrete, follow one lot of imported resin through the system:

1. The resin enters on a temporary-import pedimento, which opens the lot in the entries module against its fracción arancelaria and quantity.
2. As production runs, the system draws that lot down against the bill of materials for each finished good, recording how much resin each unit consumed, plus mermas (process waste) and desperdicios (scrap).
3. When the finished goods are returned abroad on an export pedimento, the system discharges the corresponding resin, closing the loop.
4. Any resin still unconsumed or unreturned at the end of its permanence window has to be discharged another way, by régimen change or definitive import with duties paid, or it becomes an open exposure.

The loop closes only when every step is recorded accurately and on time. One untracked scrap rate or one late export entry leaves resin "open" in the system that physically left the plant months ago.

2026 raised the stakes. The customs reform published in the Diario Oficial de la Federación (DOF, Mexico's federal gazette) on November 19, 2025, in force January 1, 2026, requires inventory control systems to be permanent and interoperable with the customs electronic system, with continuous remote access for the authority.

The obligation to keep automated inventory control has existed for years. What changed in 2026 is the authority's view of it: with a permanent, interoperable system, the SAT sees your discharges continuously and can act on them without opening a formal audit.

Common mistake. Reconciling Anexo 24 once a month and calling the inventory controlled. The reform's standard is a permanently current system. A discharge that is correct on the 30th and wrong for the preceding twenty-nine days is an exposure the authority can now see.

Why Anexo 24 decides your SAT audit

The consequence chain is what makes this an executive concern. If the system cannot demonstrate that a temporary import was returned or otherwise discharged, the SAT can determine that the goods were, in effect, definitively imported. That determination triggers the retroactive Impuesto General de Importación (IGI, the general import duty) that was deferred, plus the Impuesto al Valor Agregado (IVA) owed on entry for companies without certification, plus recargos (surcharges) and inflationary updating.

Then comes the penalty, and here the 2025 reform bites. Article 178, fracción III of the Ley Aduanera now carries a fine of 250% to 300% of the commercial value of the goods for the temporary-import infractions it covers, raised from the 70% to 100% range that applied before the reform. A separate provision, Article 185-A, sanctions the failure to keep the automated inventory control system itself. Beyond any single fine sits the larger risk: suspension or cancellation of the IMMEX program and removal from the Padrón de Importadores (the importers' registry), which stops the operation from importing at all.

In our work across the corridor, clearance problems that look like a broker issue usually trace back to inventory control upstream. Across more than 190,000 customs operations a year at 39-plus ports, the operations that pass a SAT review without disruption are the ones whose Anexo 24 was already current the day before the review landed.

Five Anexo 24 points to settle before an audit

The first is ownership. The obligation belongs to the importer, written into Article 59 of the Ley Aduanera, and the broker supports it. The 2025 reform widened the broker's own exposure to responsabilidad solidaria (joint and several liability), so scrutiny rose on both sides of the relationship.

The second is frequency. Monthly reconciliation was a defensible habit before 2026. Against a permanent, interoperable standard, the system has to be current every day.

The third is timing. A cleared pedimento only opens the entry. The risk lives in the discharge, which happens months later and which the pedimento does not record.

The fourth is the ERP. Your ERP tracks value and accounting. Anexo 24 tracks customs discharge against the pedimento and the bill of materials. The two diverge in normal operations, and that divergence is precisely what an audit surfaces.

The fifth is scope. Anexo 24 and Anexo 31 each need their own control, and managing only one leaves half your exposure unmanaged.

Quick check. Pull your three oldest open temporary imports. For each, can you show the pedimento that opened it and the document that discharged it, whether a return, a destruction, a régimen change, or a definitive import? Any import open past its permanence window with no discharge on record is the first thing an audit finds, and now the first thing a continuous system exposes.

When to bring in a customs broker to audit Anexo 24

A full Anexo 24 review earns its cost at specific moments: after rapid IMMEX expansion, after an ERP migration, after a change of customs broker, after an acquisition, or when more than twelve months have passed since anyone reconciled the system against what the SAT expects. A serious review looks for open temporary imports past their windows, mismatches between bill-of-materials consumption and recorded discharges, gaps in the catálogos, and missing discharge documentation, including fixed assets under IMMEX. Left alone, those findings become retroactive assessments. Our step-by-step guide on how to audit your Anexo 24 before SAT does covers the review in detail.

Anexo 24 is the operational backbone of the duty deferral that makes your manufacturing viable, and since 2026 the authority can watch it continuously. Treat it as infrastructure. If your last full reconciliation is more than a year old, that is the review to run before the SAT runs it for you. Talk to a Joffroy expert about an Anexo 24 audit-readiness review for your operation.

TRADE. UNDER CONTROL.

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