Taiwan → Mexico: IMMEX, Anexo 24 & Inventory

When a Taiwanese manufacturer plans a new plant in Mexico, IMMEX is often treated as a customs workstream: obtain the program, arrange imports, and let the plant, customs broker or external advisers handle the rest.

Once production starts, the real issue is usually not whether the company “has IMMEX.” It is whether physical inventory, ERP movements, customs records, production consumption, temporary-import balances, tax accounts and Taiwan HQ management reporting reconcile to the same operating facts.

ASCG Pacific’s Taiwan-to-Mexico expansion and plant setup service treats these items as one operating model. Before the first machinery and materials arrive, the legal entity, IMMEX structure, logistics, BOMs, inventory, costing, intercompany flows and headquarters reporting should be designed on the same blueprint.

Core principle: IMMEX is not a permit that can be obtained and then handed over to the customs team. In a manufacturing business it reaches directly into part numbers, BOMs, warehouses, production movements, customs, costing, tax and month-end close. If those data sources do not share a common logic from the beginning, “ERP says the material is gone, customs still shows a balance” becomes a recurring control problem.

Start with the right view of IMMEX: an export-manufacturing operating framework, not simply an import benefit

Mexico’s IMMEX program allows qualifying companies to temporarily import goods used in export manufacturing or export services, subject to the applicable customs, duty, VAT/excise and return or other lawful-destination rules.

For a Taiwanese manufacturer, the strategic value is not merely obtaining an authorization number. It is the ability to design cross-border material flows around a Mexico production model.

That design links areas that companies often manage separately:

which raw materials, components, packaging, molds and equipment enter Mexico and under what customs treatment;
which Mexican entity acts as importer of record;
which part numbers enter which BOMs;
when materials are received, transferred, issued to production, scrapped or returned;
how finished-goods exports or other lawful destinations discharge the underlying temporary imports;
how temporary-import balances and permitted periods are monitored;
how VAT/excise credits or guarantees are controlled; and
whether the inventory, COGS, WIP, fixed assets and intercompany balances seen by Taiwan HQ can be traced back to the same transactions.

This is why IMMEX should not be “added” by the customs team shortly before production launch.

Before the IMMEX approval, the plant data model is already taking shape

Current Secretaría de Economía IMMEX application information requires businesses to describe matters such as the production process, expected imports and exports, facilities, equipment, employees, capacity and investment. Depending on the case, the application and supporting process can also touch the location and control of plants, warehouses, machinery and temporarily imported goods.

The management implication is straightforward: the operating description used to obtain the program should be consistent with the ERP, customs data and actual production process that will exist after launch.

Before Taiwan HQ approves Mexico systems and master data, it should determine at least:

whether Taiwan and Mexico use the same part numbers and, if not, how they are mapped;
how commercial, customs and production units of measure convert;
how raw materials, semi-finished goods, finished goods and packaging are classified;
whether the Mexico BOM reflects the actual Mexico process rather than simply copying a Taiwan BOM;
how scrap, yield loss, rework and substitute materials are recorded;
which items are fixed assets and which are consumable tools or materials;
how plants, outside warehouses, third-party processors and submaquila locations are coded; and
how dates, quantities, currencies, exchange rates and transaction IDs can be traced across systems.

If these fields are first reconciled after mass production begins, the organization usually creates recurring Excel workarounds instead of repeatable controls.

Anexo 24 is not just “having software”; it is the ability to trace imports through consumption and discharge

Under the 2026 General Foreign Trade Rules, Anexo 24 governs the automated inventory control system. For applicable IMMEX operations, the objective is to maintain a data structure and movement history capable of tracing temporarily imported goods, not merely to produce a month-end inventory report.

The current Anexo 24 framework includes company information, material and product catalogs, and records or modules around imports, exports/outflows, balances, material consumption, discharge and adjustments. More advanced SECIIT environments require even closer links between corporate systems and customs-control information.

For Taiwan HQ, the practical question is:

Can the Mexico plant take a temporarily imported material and explain when it entered, where it is, which product consumed it, how much was actually consumed and which export or other lawful destination ultimately discharged it?

If the answer depends on three departments exporting spreadsheets and manually stitching them together, the control architecture remains fragile.

A 2026 terminology trap: the current SCCCyG is Anexo 30, even though many teams still say “Anexo 31”

Many IMMEX teams, software vendors and advisers still use the historic shorthand “Anexo 31.” The market terminology is common, but under RGCE 2026, the Sistema de Control de Cuentas de Créditos y Garantías (SCCCyG) is contained in Anexo 30.

This is more than a naming detail. SCCCyG is the SAT system used to administer and control certain VAT/excise tax credits and guaranteed amounts arising from temporary imports under the applicable IVA/IEPS certification or guarantee mechanisms.

The current rules include information such as initial inventory and discharge reporting. For companies using an IVA/IEPS certification or a guarantee, customs movements therefore need not only to be explainable through Anexo 24; they may also need to reconcile to the relevant SCCCyG credit or guarantee balances.

Taiwan HQ should not assume that “Anexo 24 is implemented” means the VAT/excise control layer is complete. The two controls have different purposes, even though they rely on overlapping underlying data.

IMMEX does not mean temporary imports automatically have zero VAT/excise cash-flow impact

This is one of the most common oversimplifications in a Mexico plant financial model.

A qualifying company that obtains the applicable Registro en el Esquema de Certificación de Empresas, modalidad IVA e IEPS may use the corresponding tax-credit mechanism for qualifying temporary imports. Companies that do not use certification may, when the applicable requirements are met, use an accepted guarantee such as a bond or letter of credit under the relevant rules.

The reverse is equally important: a company should not set every temporary import’s IVA/IEPS cash-flow impact to zero simply because it has an IMMEX program.

The financial model should separately confirm:

the IMMEX authorization itself;
whether IVA/IEPS certification has been obtained and which category applies;
whether a guarantee will be used instead;
whether sensitive goods have additional requirements;
how credit or guarantee balances are controlled through SCCCyG; and
what cash-flow exposure exists before the certification or guarantee structure is fully operational.

Those differences can materially change working-capital requirements during plant ramp-up.

ERP inventory, Anexo 24 inventory and financial inventory are not necessarily the same number

A common headquarters question is: “How much inventory does the Mexico plant have?”

For an IMMEX manufacturer, there may be at least four valid answers:

Physical inventory — what is actually in the warehouse and production areas.
ERP inventory — what the system records after receipts, transfers, production issues and completions.
Customs inventory — temporary imports that remain open in Anexo 24/customs control and have not yet been discharged.
Financial inventory — the balance-sheet amount after applying ownership, cut-off, costing and accounting-recognition rules.

These numbers do not have to be identical at every moment. The control question is whether differences are explainable, measurable and traceable.

Examples include:

materials physically received before the ERP receipt is posted;
ERP backflush moving material into WIP before the customs discharge is completed;
consigned material physically in Mexico while legal ownership remains with the Taiwan parent;
production scrap recorded operationally before customs and financial treatment catches up;
goods that have left the plant while export documentation is still being processed; or
unit-of-measure or BOM-version differences creating quantity variances across systems.

A mature IMMEX control environment does not pretend timing differences will never exist. It creates a month-end reconciliation that identifies each difference, owner, amount, root cause and expected clearing date.

Taiwan HQ needs a consolidatable manufacturing reporting package, not another Mexico spreadsheet

If the Mexico plant forms part of a Taiwanese group’s North American supply chain, headquarters usually needs more than local statutory financial statements.

A useful monthly management package should be able to explain:

raw material, WIP and finished-goods balances;
inventory by plant, warehouse and third-party location;
which goods remain under temporary import and which have been returned or discharged;
aging and exceptions within temporary-import balances;
which inventory belongs to the Mexico entity and which remains owned by the Taiwan parent or another related party;
standard-cost versus actual-cost variances;
allocation of freight, duty, brokerage and other landed-cost elements;
scrap, yield, rework and inventory-adjustment trends;
machinery and fixed-asset imports, capitalization and location;
Taiwan-Mexico intercompany AP/AR, goods in transit and uninvoiced items;
MXN, USD and TWD foreign-exchange effects; and
IVA/IEPS credit, guarantee or other material customs-related balances.

If this information is assembled only once a year for the audit, it cannot support ramp-up, margin, working-capital or supply-chain decisions.

A stronger design establishes a recurring Mexico local close → customs reconciliation → Taiwan HQ reporting sequence before go-live.

IMMEX and USMCA origin are separate questions

Another common assumption is: “The product is manufactured in Mexico under IMMEX, so it should qualify for USMCA treatment when exported to the United States.”

That conclusion is not automatic.

IMMEX is a Mexican manufacturing/export and temporary-import program. USMCA preferential tariff treatment depends on whether the product satisfies the applicable rules of origin. A product can be manufactured in Mexico without qualifying as an originating good for preferential tariff treatment.

The company therefore needs product-specific analysis based on factors such as:

tariff classification;
tariff-shift requirements;
regional value content;
special industry rules;
non-originating materials;
BOM and supplier changes; and
documentation supporting the origin claim.

This also means BOM governance affects production, Anexo 24, costing and USMCA origin analysis at the same time. If Taiwan HQ changes a supplier or substitute material, the Mexico team should not update ERP alone while ignoring customs and origin consequences.

The 2026 USMCA review process has also kept rules of origin and North American supply-chain integrity at the center of bilateral discussions, making disciplined origin governance particularly relevant for Asian manufacturers using Mexico as part of a North American production footprint.

IMMEX also has an annual management gate before the end of May

IMMEX is not a one-time authorization that can be ignored after approval.

Program holders must submit the Reporte Anual de Operaciones de Comercio Exterior (RAOCE) for the preceding fiscal year by the applicable deadline, generally the last business day of May. Failure to maintain the annual reporting and other program conditions can result in suspension and, if not corrected within the applicable cure period, cancellation.

For Taiwan HQ, this belongs in the group compliance calendar rather than in one customs employee’s personal reminders.

Annual governance should verify at least:

that RAOCE sales and export data can be produced consistently by finance and customs;
that RFC, e.firma, registered addresses and other program-maintenance items remain valid;
that SAT compliance issues are not creating a program risk; and
that the plant’s actual operations remain within the approved IMMEX scope.

Four common Taiwan-to-Mexico manufacturing scenarios require different controls

Scenario A: Taiwanese electronic components enter Mexico, are assembled and exported to the U.S.

This model often combines high SKU counts, engineering changes, substitute materials and frequent exports.

The control objective is not only pedimento quantity. Taiwan shipment, Mexico receipt, BOM consumption, finished-goods output, export, Anexo 24 discharge and USMCA-origin data should form one traceability chain.

If IVA/IEPS certification or a guarantee is used, SCCCyG balances and discharge information become an additional reconciliation layer.

Scenario B: Taiwan HQ sends production equipment, tooling and molds to Mexico

Equipment can involve temporary import, asset ownership, capitalization in Mexico, depreciation, intercompany use or leasing arrangements and physical-location controls.

The group fixed-asset register, Mexico accounting records, customs data and physical asset tagging should be connected from the day the equipment enters the plant. Otherwise, relocation, disposal or return several years later becomes difficult to support.

Scenario C: the Mexico plant uses third-party warehouses or submaquila

Once temporarily imported material leaves the principal plant, location control becomes more important.

The company should know which goods are at each permitted or applicable location, who controls them, when they move, which process they enter and how the customs and system records are updated. A consolidated inventory value alone can hide location-level compliance risk.

Scenario D: goods are physically in Mexico while ownership remains with a Taiwan group company

Consignment and other cross-border ownership structures separate physical location from accounting ownership.

Without clear ownership codes, Mexico ERP, Taiwan consolidation, transfer-pricing analysis, customs value and working-capital reporting can each use different assumptions.

The group should define who owns the goods, when title transfers, who bears risk, who invoices and how every system reflects the arrangement.

A 12-point readiness check for Taiwan HQ before Mexico plant go-live

What role does the Mexico entity, Taiwan parent and each related party perform?
Which entity is importer, manufacturer, exporter and customer-facing company?
Does the IMMEX application match the actual manufacturing flow?
Are material, semi-finished, finished-goods, packaging and fixed-asset master data defined?
Are Taiwan and Mexico part numbers, UOMs, BOMs and tariff classifications mapped?
Can ERP movements support Anexo 24 traceability?
How are scrap, rework, substitutions, adjustments and physical-count variances approved and recorded?
Is the IVA/IEPS certification, guarantee or actual payment route reflected in the cash-flow model?
If SCCCyG applies, who owns initial inventory, credit/guarantee balance and discharge reporting?
Is USMCA origin analysis performed separately for products manufactured in Mexico and exported to the U.S.?
How will physical, ERP, customs and financial inventory be reconciled at month end?
Can the Taiwan HQ package show ownership, aging, cost, intercompany exposure and customs exposure?

If half of these questions are still answered with “we will fix it after the plant starts running,” the operating model is not truly ready.

A more resilient Taiwan → Mexico plant implementation sequence

Phase 1: Operating model

Map material flow, legal ownership, contract flow, shipping, manufacturing, export destinations and the intercompany model.

Phase 2: IMMEX + customs design

Confirm IMMEX scope, import categories, tariff classifications, relevant locations/warehouses, broker process, Anexo 24 architecture and the planned IVA/IEPS certification or guarantee route.

Phase 3: ERP + master data

Build part master, BOM, UOM, warehouse, production movement, scrap, fixed assets and customs identifiers into the system design. Avoid creating Anexo 24 as a completely parallel manual universe outside ERP.

Phase 4: Finance + intercompany

Establish chart of accounts, inventory valuation, standard/actual costing, intercompany coding, FX, landed cost, AP/AR reconciliation and Taiwan HQ reporting mapping.

Phase 5: Go-live controls

Before the first significant temporary imports, test the entire receipt → production → shipment → export → discharge chain, including exception handling.

Phase 6: Recurring governance

Run monthly inventory/customs reconciliations, SCCCyG reviews when applicable, the RAOCE annual calendar, program maintenance, USMCA-origin governance and HQ management reporting.

When is an integrated readiness review especially valuable?

It is particularly useful when:

the Taiwanese group is establishing its first manufacturing entity in Mexico;
the plant will import significant components from Taiwan, China or Southeast Asia;
IMMEX and IVA/IEPS certification or guarantee mechanisms are planned;
SKU, BOM, substitute-material and engineering-change activity is high;
products will primarily be exported to the United States and require separate USMCA-origin analysis;
third-party warehouses, submaquila or multiple plant locations will be used;
ownership of equipment, tooling or consigned inventory remains in Taiwan;
the Mexico ERP will integrate with Taiwan SAP, Oracle or another group platform; or
the Taiwan CFO expects reliable inventory, margin, cash and intercompany reporting from the first full month.

ASCG Pacific can start with the Taiwan-to-Mexico expansion and plant setup operating model and coordinate Mexico tax and accounting, IMMEX/inventory data, intercompany transactions and Taiwan HQ reporting. Where the group also has a U.S. sales company or a multi-entity North American structure, the model can be extended through our Asia–U.S.–Mexico cross-border coordination framework so supply-chain, customs and finance teams do not operate from different versions of the same transaction facts.

Official references

This article reflects official rules and government information available through August 2026 and is intended as general business, customs, tax and operating information. IMMEX, IVA/IEPS, origin, customs, tax and legal treatment should be confirmed against the company’s actual goods, transactions, certification status and operating facts.

This article provides general information only and is not tax, legal or accounting advice for any specific facts or circumstances.