The Annex 24 inventory control system is the mandatory electronic ledger every company operating under Mexico’s IMMEX (Maquiladora) program must keep, tracking each temporarily imported item from border entry through its exit as a finished export, destruction, or other authorized disposition. It exists so customs authorities can verify, in real time if needed, that duty-free goods are being used as promised and not diverted into the domestic market. If your system doesn’t meet the standard, Article 59 of the Customs Law allows authorities to treat every good in your possession as foreign merchandise without legal status in Mexico.1Agencia Nacional de Aduanas de México. Obligaciones de los importadores
Rule 4.3.1 of the General Rules for Foreign Trade specifies what the system has to contain: at minimum, the catalogs and modules established in Annex 24, Section I.2Bado.mx. Rule 4.3.1 – Minimum Information on Inventory Control (Annex 24) Manual logs and paper ledgers do not qualify. The system has to be fully operational from your first temporary import.
What the System Must Contain
Annex 24 is built around several interconnected modules. Compliant software must include at least:
- A general inventory catalog with all goods and materials to be temporarily imported, the SAT-registered facilities where they will be stored and processed, and the finished products destined for export.
- A customs module tracking the specific customs details of every temporary import, including used materials, exits (exports, destructions, donations), and fixed assets, automatically deducting material quantities and following scrap or waste to final disposition.
- A used materials module that mirrors the production process registered under the IMMEX program, cross-referencing finished-goods volumes against actual component consumption and resulting scrap based on each product’s bill of materials.
- A reports module that generates entries reports, exits reports, balance reports, and used materials reports for internal management and government audits.
Each raw material needs a unique part number, technical description, and tariff classification code before it reaches the border. Units of measure must be recorded consistently across every transaction. Fixed assets such as machinery and industrial tools need individual catalog entries with serial numbers and brand details. Supplier and customer data modules capture names, tax IDs, and physical addresses for every trading partner.
That level of detail is what lets the system calculate exactly how much raw material goes into each finished product and whether the quantities leaving Mexico match what came in. Errors in the part number database are one of the most common causes of customs delays and miscalculated tax liabilities.
Pedimentos, Discharges, and the PEPS Method
The backbone of the system is its integration with pedimentos, the official customs declarations. Every temporary import pedimento creates an open entry that must eventually be closed by an export pedimento or another authorized exit. Closing an entry is called a descargo (discharge), and the system subtracts the volume of exported material from the original import balance.
The default depletion method for discharges is PEPS (Primeras Entradas, Primeras Salidas), the Spanish equivalent of First In, First Out. The oldest imported materials are legally assumed to be the first consumed in production and exported. Unless a company holds specific authorization to use a different method, the software applies this logic automatically.
Discharge tracking is where most compliance failures start. Every gram of material needs an unbroken chain of documentation from import pedimento to production consumption to export pedimento. If the quantities do not reconcile, you have unaccounted foreign merchandise sitting in your facility with no legal justification.
The 48-Hour Reporting Rule
Companies registered under the Company Certification Scheme have to transmit specified data electronically within 48 hours of importing goods into Mexico, and customs authorities have to be given online access to verify temporary import controls and the return of goods in real time.3International Trade Administration. Mexico Customs Inventory Control Update
That window means data entry has to sit inside daily receiving operations, not weekly cleanup shifts. A shipment cleared on Monday morning needs to appear in the system by Wednesday morning. Late entries throw off discharge calculations, which distort balance reports, which is exactly what triggers deeper scrutiny during an audit.
How Long Temporary Imports Can Stay
Temporary imports do not have an indefinite shelf life. Raw materials and components used in manufacturing generally must leave Mexico within 18 months of their import date. Machinery and equipment can typically remain for the duration of the IMMEX authorization, but consumable inputs face the shorter deadline.
The Annex 24 system has to track these deadlines automatically and flag materials approaching expiration without a corresponding export discharge. Once the authorized period expires, the tax benefit disappears and the full import duty, VAT, and any applicable compensatory fees become payable. Unresolved credits sitting in the system past the legal deadline turn into immediate tax liability.
Feeding Into Annex 31 for VAT-Certified Companies
If your company holds a VAT and IEPS certification (Certificación IVA e IEPS), Annex 24 feeds a second compliance layer called Annex 31. Annex 31 runs through the SAT’s SCCCyG platform (System for Control of Accounts for Credits and Guarantees), which monitors the tax credits tied to temporary imports.
Discharge reports generated from Annex 24 are the basis for clearing credits in the Annex 31 account. Companies submit a discharge report to the SAT portal each month covering all temporary imports resolved in that period. Any inconsistency between the internal Annex 24 inventory data and the external Annex 31 fiscal account is treated as a serious red flag.
Errors in part numbers, customs values, quantities, or reporting dates can produce mismatches that leave credits unresolved. Regular reconciliation between the two systems catches deviations in discharge reports, spots missing operations, and helps prepare defensible responses when the SAT questions specific VAT credit claims.
Fixing Merchandise That Overstayed
When goods exceed their authorized temporary import period, Mexico’s General Rules for Foreign Trade offer a regularization procedure that converts them into definitive imports by paying the taxes that should have applied from the start.
The process requires filing a definitive import pedimento with the appropriate classification codes. The company pays the general import tax, compensatory fees, and VAT, plus updates and surcharges calculated from the month the goods were originally imported through the payment date. The customs value from the original temporary import pedimento is the basis for these calculations.4Bado.mx. Rule 2.5.2 – Regularization of Expired Temporary Imports and Waste
Regularization is still available even after customs authorities have begun a verification. In that case, the company must notify the authority in writing of its intention to definitively import the goods and has 20 days from that notification to file the definitive import pedimento, along with the fines for exceeding the return period.4Bado.mx. Rule 2.5.2 – Regularization of Expired Temporary Imports and Waste The option disappears once the merchandise has been formally seized and become property of the federal tax authorities.
For scrap and waste, the tariff classification at the time of definitive importation is used instead of the original classification, with contributions based on current commercial value. Preferential tariff rates from trade agreements can still apply during regularization if the goods qualify as originating and a valid proof of origin is available.
Recordkeeping and What Non-Compliance Costs
Mexico’s Federal Tax Code requires taxpayers to keep their accounting and customs records for at least five years from the date the relevant tax return was filed. The statute of limitations on tax authority review is five years in standard situations but extends to ten years when the taxpayer failed to keep required records or never filed a return.5PwC Worldwide Tax Summaries. Mexico – Corporate – Tax Administration Losing Annex 24 records early does not just create a documentation gap; it extends the government’s enforcement window.
Financial penalties are expressed as multiples of Mexico’s UMA (Unidad de Medida y Actualización), so they adjust upward each year automatically. Specific fine amounts vary by violation: missing records, inaccurate classifications, or failure to produce reports during an inspection each carry their own exposure.
The most severe consequence is suspension or cancellation of the IMMEX program itself. The SAT can cancel IMMEX registration for a range of failures, including not maintaining the documentation supporting foreign trade operations, submitting false or altered documentation, not having the infrastructure to carry out maquila operations, or failing to allow government audits.6Jadelrio. Cancellation and/or Suspension of the IMMEX Program The importer registry can also be suspended when a company fails to keep required accounting records, books, or inventories in line with tax and customs provisions. Customs fraud involving deliberately falsified records can carry criminal liability under the Federal Tax Code.