Blog | Prodensa

What Years of IMMEX Operations Have Taught Me About Annex 24

Written by Maria Elena Sierra | Mar 31, 2026 6:11:50 PM

Throughout my time at Prodensa, I have had the opportunity to closely observe the evolution of hundreds of manufacturing operations in Mexico. Along this path, the topic of Annex 24 consistently emerges in boardrooms and on the shop floor alike.

Often (more than I’d like, if I’m honest) companies operating under the IMMEX program see Annex 24 simply as a regulatory compliance requirement, a "necessary evil," or just another administrative task. However, my perspective is  very  different. In practice, Annex 24 is much more than an obligation; it is the pulse of a company’s operational and commercial health. It is the system that tracks the full life cycle of temporarily imported goods: from the moment they cross the border, move through the production line, until they are ultimately exported or returned.

 

When Your System Stops Telling the Truth

The real challenge we are seeing today is not the lack of software systems, as most companies have robust tools in place. The problem arises when, over time, those systems stop reflecting the operational reality of the business.

It is common for small inconsistencies to appear between production records, inventory systems, and the customs information reported to authorities. These discrepancies are often silent and can go unnoticed for months or even YEARS, but they tend to surface at the least opportune moment: during an audit or a review by the authorities.

 

If These Four Don’t Match, You Might Have a Problem

To maintain a “healthy” Annex 24, at Prodensa we promote a practical approach that I consider essential for any IMMEX operation: four-way reconciliation. This exercise is a control discipline that ensures four critical sources of information tell the same story:

  1. The ERP or MRP: This is the heart of the operation. It is where the reality of purchasing, inventory movements, and material consumption lives.
  2. The inventory control system (Annex 24): This is the engine that calculates customs balances based on Bills of Materials (BOM) and discharges.
  3. The physical inventory: What is actually on the floor, in warehouses, and in work in process (WIP). If the system shows 100 units but physically there are 80, there is a compliance gap.
  4. Data Stage (Official Data): The information the authority has about us through customs entries.

When we compare these four sources regularly, we gain invaluable visibility. It allows us to confirm that our declarations to customs match what is actually happening in the plant.

 

When the Numbers Don’t Match, It’s Never Random

In my experience, when differences are identified, the causes are rarely intentional; they are usually operational. We are talking about outdated Bills of Materials (BOM), inconsistencies in units of measure across systems, incomplete master data, or scrap and waste that were not properly recorded.

Identifying these issues in time allows us to make strategic decisions, such as whether a customs entry correction is required or whether adjustments in internal production processes are needed.

It's important to keep in mind that maintaining a healthy Annex 24 environment depends on strong operational foundations. We are talking not only about having a good traffic or logistics department, but about cross-functional collaboration:

  • BOMs must accurately reflect the current production process.
  • Units of measure must be consistent and standardized.
  • Recording of scrap and adjustments must be rigorous.

When these elements are aligned, Annex 24 stops being a burden and becomes a strategic tool that provides confidence and visibility. For any IMMEX company, that alignment between systems, operations, and customs declarations is the only path toward a solid and, above all, sustainable compliance framework in the long term.