September 24, 2026
The deadline to file with the Mexican Social Security Institute («IMSS») the audit report («dictamen») on compliance with social security obligations for fiscal year 2025 is September 30, 2026, in accordance with Article 161 of the Regulation of the Social Security Law on Affiliation, Classification of Companies, Collection and Enforcement («RACERF», for its Spanish acronym).
Pursuant to Article 16 of the Social Security Law («LSS», for its Spanish acronym), employers that had an annual average of 300 or more employees during fiscal year 2025 are required to have their compliance with IMSS obligations audited by an Authorized Public Accountant (the «Accountant»). Employers that do not meet this threshold may voluntarily elect to have their obligations audited.
The audit report must be prepared by the Accountant and filed through the IMSS Electronic Audit Report System («SIDEIMSS»). To carry out the corresponding procedures in the system, the Accountant and the employer, obligated party or, as applicable, its legal representative must have a valid e.firma (advanced electronic signature).
Given the approaching deadline, we recommend that employers required to file an audit report, as well as those that filed the notice to do so voluntarily:
- File the audit report ahead of the deadline, in order to reduce the risk of rejections or technical failures.
- Verify the status of their employer registration numbers, particularly that none has a «No localizado» («Not Located») or «Suspendido» («Suspended») status and, if applicable, clarify such status with the IMSS Subdelegación (local office) that controls the employer registration number before filing the audit report.
- Confirm the validity of the e.firma certificates of the Accountant and the employer, obligated party or legal representative involved in the filing.
- Use the current versions of the SIDEIMSS tools and templates. IMSS indicates that the most recent version of the template must be used to generate the files corresponding to the employer information section.
- Retain the electronic filing acknowledgment and verify that the filing has been successfully completed in the system. For online filings, IMSS states that the acknowledgment generated when preparing and filing the audit report replaces the cover letter.
If, due to an act of God or force majeure, or duly substantiated physical or legal limitations, it is not possible to file the audit report within the applicable deadline, Article 162 of the RACERF allows the employer to request from IMSS an extension of up to forty business days, provided that the request is filed before the deadline and is signed by the employer or its legal representative and by the Accountant. It is important to note that, under the same provision, an audit report filed outside the deadlines established in the RACERF will have no legal effect unless IMSS determines that there are grounds to accept it.
For assistance with issues related to SIDEIMSS, IMSS maintains the following email address: soporte.dictamen@imss.gob.mx.
Our Social Security team remains available to provide advice regarding compliance with this obligation and to assist with any issue that may arise in connection with the filing of the audit report.
Sincerely,
Gil Zenteno
Gabriela Méndez
Jesús Carmona