IMSS incorporates EMA and EBA proposals into the IMSS Mailbox: new consultation and reconciliation mechanisms

This measure forms part of the Institute’s modernisation and digitalisation initiatives and aims to facilitate employers' access to the information used to determine employer and employee social security contributions, housing fund contributions and loan repayments. 

What is changing? 

Through the "My Documents" section of the IMSS Mailbox, employers will be able to view and download the following proposals: 

• EMA (Advance Monthly Assessment) 
• EBA (Advance Bi-monthly Assessment) 

These formats will complement the information currently available through payment files and files uploaded to the Single Self-Assessment System (SUA). 

Effective date 

The Agreement establishes that it will enter into force on 9 October 2026. 

However, the Institute must first implement the necessary technological adjustments to ensure its proper deployment and operation within the IMSS Mailbox. 

Scope of the measure 

It is important to note that this provision: 

Facilitates employers’ access to relevant information. 

Centralises document consultation within a single platform. 

Enables improved reconciliation of information between IMSS and the SUA. 

Supports the early identification of discrepancies or inconsistencies before the payment of social security contributions and housing fund obligations. 

Reduces the administrative time associated with obtaining assessment proposals. 

However, the measure does not modify: 

The determination of employer and employee social security contributions. 

Contributions to INFONAVIT. 

Housing loan repayments. 

Existing payment deadlines and procedures. 

Its purpose is exclusively operational and aimed at improving access to information. 

Benefits for employers 

The incorporation of EMA and EBA proposals into the IMSS Mailbox provides several operational benefits, including: 

Electronic access to and download of information from a single portal. 

Simplification of administrative processes. 

Greater control and visibility over the information used by IMSS to determine contributions. 

Early identification of inconsistencies between institutional records and employer-calculated data. 

Support for reconciliation processes prior to generating payments in the SUA. 

Increased efficiency for employers with multiple employer registration numbers. 

Recommendations 

In light of the implementation of this measure, we recommend that employers: 

Verify that they have active access to the IMSS Mailbox. 

Periodically review the "My Documents" section. 

Implement reconciliation procedures between the information contained in the EMA and EBA proposals and the data recorded in payroll records and the SUA. 

Promptly address any discrepancies identified before determining and paying contributions. 

Keep their IMSS electronic communications channels up to date. 

Final considerations 

The incorporation of the Advance Monthly Assessment (EMA) and Advance Bi-monthly Assessment (EBA) proposals into the IMSS Mailbox represents a significant step forward in the Institute’s digitalisation strategy and strengthens employers’ self-correction and preventive compliance mechanisms. 

Although the measure does not modify social security obligations or the methodology used to calculate contributions, it provides an additional tool that can support more efficient reconciliation processes, facilitate the timely identification of discrepancies and reduce the risk of subsequent assessments or observations by the authorities. 

Interested in learning more about this topic? Our team is ready to support and guide you.