Mexico Replaces the IMSS Digital Certificate with e.firma for Electronic Filings

The Mexican Social Security Institute (Instituto Mexicano del Seguro Social or IMSS) published Resolution ACDO.AS2.HCT.290626/176.P.DIR in the Official Gazette of the Federation on July 16, 2026, which eliminates the use of the Employer Electronic Identification Number and its digital certificate.

In their place, the resolution establishes the Advanced Electronic Signature (e-signature or e.firma) issued by the Mexican Tax Administration Service (Servicio de Administración Tributaria or SAT) as the only accepted authentication method for electronic procedures with IMSS. The resolution takes effect on October 14, 2026. Companies should take proactive measures before this date to avoid disruptions to their payroll operations and compliance with IMSS obligations.

Employers that currently use the IMSS digital certificate for electronic procedures must switch to a valid SAT-issued e.firma. Starting October 14, 2026, the e.firma will be required for employee registrations and terminations, salary changes and other electronic processes before the IMSS that require authentication.

To avoid disruptions to payroll and the filing of employee affiliation changes with the IMSS, companies should take the following steps:

• confirm that the company's e.firma is valid
• ensure that the legal representative's e.firma is valid
• link both e.firmas in the IMSS Virtual Desktop
• keep the necessary supporting documents on hand

If companies do not complete the transition in time or do not have the required e.firmas and links, they may have difficulty electronically filing employee registration changes with the IMSS. Companies may also face payroll delays and fall behind in meeting their social security obligations.

For additional information or questions, please contact the authors.

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