Implementation of the e.firma as the only valid means for electronic affiliation movements before the IMSS

On July 16, 2026, Agreement ACDO.AS2.HCT.290626/176.P.DIR, issued by the H. Technical Council of the Mexican Social Security Institute (IMSS) in an ordinary session held on June 29, 2026, was published in the Official Gazette of the Federation (DOF).

The Agreement establishes the exclusive use of the Advanced Electronic Signature (e.firma), issued by the Tax Administration Service (SAT), as the only valid digital certificate for carrying out affiliation movements before the IMSS by electronic means and for the linking of legal representatives.

Key points of the Agreement

1. The e.firma, whose digital certificate is issued by the SAT (Mexican Tax Administration Service), is the only valid means for employers or obligated parties to conduct transactions with the IMSS (Mexican Social Security Institute) through electronic means. Documents signed with an e.firma will have the same legal effect and evidentiary value as those presented with a handwritten signature.
2. The linking of legal representatives exclusively through the IMSS Virtual Office, the representative will authenticate with their own e.signature and will sign jointly with the represented person, both using their respective e.signature.
3. The Agreements that regulated the previous scheme of digital certificates of the IMSS were repealed.
4. The use of the Electronic Employer Identification Number (NPIE) and its digital certificate issued by the IMSS is repealed, so it will no longer be a valid means of authentication before the Institute once the transition period is over.
5. A transition period of 90 calendar days is established, starting from the publication of the Agreement in the DOF (July 16, 2026), the deadline to complete the migration is October 13, 2026.
6. The agreement comes into effect the day after its publication in the DOF, that is, on July 17, 2026.

Main risks for obliged persons

• Companies whose e.firma has expired will not be able to carry out affiliation movements in a timely manner.
• If legal representatives are not properly linked to the Virtual Desktop, they may be unable to submit electronic procedures.
• The loss, revocation, or cancellation of the e.firma may halt operational processes related to registrations, terminations, salary modifications, and other transactions with the IMSS.
• If you try to continue using the NPIE after the transition period, you could face rejection of your applications.
• To commit breaches.

Practical recommendations for employers

Inform and train the areas responsible for affiliation movements about the new authentication scheme to ensure operational continuity.

Verify the validity of the e.signature of both the employer and their representatives, agents or administrators.

Perform the linking in the Virtual Desktop of legal representatives in the Virtual Desktop of the IMSS, using joint authentication with e.firma (of the representative and the represented).

Plan your migration in advance, allowing enough time to address potential technical or administrative issues; the deadline is October 13, 2026.