Construction workers social security regulation (Reglamento del Seguro Social para los Trabajadores de la Construcción) · IMSS SIROC agreement (Acuerdo SIROC) · Social Security Law (Ley del Seguro Social, LSS) article 15 A
SIROC compliance, in the same file as your REPSE records
Every construction project (obra) and every phase with its registration number, its reported changes (incidencias) and its acknowledgement of receipt. The deadlines of the Mexican Social Security Institute (IMSS), counted project by project, with reminders before they fall due. On the REPSE side, the file RepseShield already keeps up to date all year.
REPSE and SIROC are already linked. Since September 1, 2021, a subcontractor performing specialized construction work (subcontratista de ejecución de obra especializada) declares, in the SIROC project registration (registro de obra) itself, its REPSE number (Número de REPSE), the purpose of the specialized work and the approximate number of workers who will take part. The IMSS joined the two registries on its own initiative, in the same form and before the same authority.
What the IMSS requires on a construction project
| Obligation | Deadline | Legal basis |
|---|---|---|
| Register the project or the phase with the IMSS sub-delegation office (Subdelegación) for its location | 5 working days from the start of work | Regulation, article 12 |
| Report each change (incidencia): suspension, resumption, cancellation and completion | 5 working days for each one | Regulation, article 12; Agreement, Rule One (Regla Primera) |
| Report of the amount executed to date, every two months (reporte bimestral) | Within the first 17 calendar days of January, March, May, July, September and November | Agreement, Rule One |
| Notices for workers hired for the project (registrations, terminations, salary changes) | 5 working days | Regulation, article 9 |
| IMSS review of the completed project | The Institute has 90 working days from the completion notice to review it | Regulation, article 12 A, section I |
| Provide the data, reports and documents the Institute requests | 5 working days; if they are not provided, the IMSS estimates your labor cost per square meter | Regulation, article 18 |
Each registration and each change is signed with the FIEL (advanced electronic signature). The resulting record is the acknowledgement of receipt (acuse de recibo), which carries the Institute's digital seal and which the employer may print: the rules leave it optional, so not having it is not a breach, but it is the proof you show later. Working days follow the applicable Mexican calendar.
Filing late on your own costs no fine. Being found out does
Article 304 C of the Social Security Law is the reason monitoring a project is worth money: no fines are imposed when obligations are met spontaneously after the legal deadlines. Spontaneity is lost in three ways, and all three are worth knowing:
- The IMSS discovers the omission.
- You correct it after the Institute has served an order for an on-site audit visit (orden de visita domiciliaria), a formal request (requerimiento) or any other notified action aimed at verifying compliance with your social-security obligations. A notified action about something else does not end spontaneity.
- You correct it more than 15 days after filing a report by an authorized public accountant (dictamen de contador público autorizado), for what that report found. Here your own report starts the clock, without the IMSS having done anything.
When a fine does come, reporting late, with false or incomplete data, or failing to report to the Institute the address of each construction project or project phase is fined at 20 to 350 UMA (article 304 A, section XXI, and article 304 B, section IV). At the 2026 value of the UMA (Unidad de Medida y Actualización, Mexico's legal reference unit for amounts such as fines), that is MXN 2,346.20 to MXN 41,058.50.
Stated precisely, because the difference matters: article 304 C waives the fine. Unpaid contributions, surcharges (recargos) and capitales constitutivos are still owed (Regulation, article 25). What monitoring buys you is the days between your own correction and the authority noticing, not the money for the contributions.
What RepseShield does with your projects
The project file
Every registered project and phase, with its project registration number, its acknowledgement where there is one, and the contractual relationship you entered. One place, organized the way the file requires, not the way each site manager (residente de obra) keeps it.
Deadlines, counted per project
The 5 working days for the registration and for each change, and the report due every two months within the first 17 calendar days, project by project, with no one keeping the calendar by hand.
Reminders before the due date
The reminder arrives before the date, not after. That is the difference between correcting spontaneously and having the Institute find the omission.
And on the REPSE side, business as usual
If your company sells or buys specialized services or works, those obligations already live in RepseShield and do not change because the work is construction: a current REPSE registration, checked against the public registry of Mexico's Ministry of Labor (STPS) at every payment; the ICSOE with the IMSS and the SISUB with Infonavit every four months; the evidence that the service actually took place (materialidad), which supports the Mexican income-tax deduction and the VAT (IVA) credit; preparation for an STPS inspection; and requests from the authorities with their deadline running.
What we do not cover, stated plainly
Safety and hygiene on the construction site is not our product. NOM-031 (safety committees per site, work permits, accident notices, the file shown in a safety inspection) is a whole field of its own, with a different buyer inside the company. We do not cover it, and we would rather say so before anyone assumes it.