Skip to main content

IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo)

IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo)

AVISO DE ACCIDENTE DE TRABAJO — FORMA ST-1

Instituto Mexicano del Seguro Social (IMSS) — Seguro de Riesgos de Trabajo

Ley del Seguro Social Artículo 58 | Reglamento para la Clasificación de Empresas y Determinación de la Prima en el Seguro de Riesgos de Trabajo (RACERF)

I. DATOS DEL PATRÓN

Razón Social / Nombre: [Employer Name]

RFC: [Employer RFC]

Registro Patronal IMSS: [Registro Patronal]

Domicilio del Centro de Trabajo: [Workplace Address]

II. DATOS DEL TRABAJADOR LESIONADO

Nombre Completo: [Worker Name]

NSS (Número de Seguridad Social IMSS): [Worker NSS]

CURP: [Worker CURP]

RFC: [Worker RFC]

Puesto de Trabajo: [Worker Job Title]

Fecha de Nacimiento: [Worker DOB]

Sexo: [Worker Sex]

III. DESCRIPCIÓN DEL ACCIDENTE

Fecha del Accidente: [Accident Date]

Hora del Accidente: [Accident Time]

Tipo de Accidente: [Accident Type]

Lugar Exacto del Accidente: [Accident Location]

Descripción de Cómo Ocurrió el Accidente:

[Accident Description]

Tipo de Lesión: [Injury Type]

Parte del Cuerpo Lesionada: [Injured Body Part]

Tipo de Incapacidad Esperada: [Disability Type]

IV. ATENCIÓN MÉDICA

Primeros Auxilios Brindados: [First Aid Provided]

UMF / HGZ IMSS de Referencia: [IMSS Clinic]

Testigo del Accidente: [Witness Name]

PRESTACIONES DEL SEGURO DE RIESGOS DE TRABAJO (LSS art. 58):

• Atención médica, quirúrgica, hospitalaria y rehabilitación sin costo para el trabajador

• Subsidio por incapacidad temporal: 100% del Salario Diario Integrado (SDI) desde el día siguiente al accidente

• Pensión por incapacidad permanente parcial o total según valuación médica IMSS

• Pensiones de viudez, orfandad y ascendientes en caso de defunción (LSS arts. 64–68)

IMPACTO EN PRIMA RACERF: Este aviso se incorpora al cálculo de la siniestralidad del patrón para la determinación anual de la prima de riesgos de trabajo conforme al RACERF artículo 72.

CERTIFICACIÓN DEL PATRÓN

El suscrito patrón, en nombre de [Employer Name], certifica bajo protesta de decir verdad que los datos contenidos en el presente Aviso de Accidente de Trabajo son verídicos y completos.

En [Notification City], a [Notification Date].

PATRÓN / REPRESENTANTE AUTORIZADO:

[Employer Name]

Firma: _________________________ Fecha: _________________________

TESTIGO:

[Witness Name]

Firma: _________________________ Fecha: _________________________

Este aviso debe presentarse al IMSS a través del portal IMSS IDSE o en la subdelegación correspondiente el mismo día del accidente o dentro de las 24 horas siguientes. Conserve el acuse de recibo IMSS como constancia del aviso oportuno.

Employer / Authorised Representative (Patrón / Representante Autorizado)

________________

Signature

Witness (Testigo)

________________

Signature

Maintained by Vladislav Sergienko, Founder·Template last modified: ·Report an error

What Is a IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo)?

An IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo — Forma ST-1) is the official document employers must file with the Instituto Mexicano del Seguro Social (IMSS) to report an occupational accident (accidente de trabajo) or occupational disease (enfermedad de trabajo) suffered by a registered worker, as required by the Ley del Seguro Social (LSS) published in the Diario Oficial de la Federación on 21 December 1995 and its regulatory framework under the Reglamento para la Clasificación de Empresas y Determinación de la Prima en el Seguro de Riesgos de Trabajo (RACERF), published in the DOF on 22 October 2004.

Under Article 41 of the LSS, riesgos de trabajo (occupational risks) include accidents and diseases directly caused by or as a consequence of work. Article 42 LSS defines accidente de trabajo as any bodily injury the worker suffers as a result of the force of a sudden and violent external event occurring during or in connection with work, and also includes accidents occurring during travel from the worker's home to the workplace (accidente in itinere) under Article 42 fracción II LSS. Enfermedad de trabajo under Article 43 LSS is any pathological condition caused by continuous work in conditions dictated by the nature of the employment — the IMSS maintains a catalogue of recognised occupational diseases (tabla de enfermedades de trabajo) in the LSS.

The IMSS administers the Seguro de Riesgos de Trabajo (occupational risk insurance) branch, funded exclusively by employer contributions calculated on the Salario Diario Integrado (SDI) of each worker. The employer's annual premium (prima de riesgo de trabajo) is determined through the RACERF formula based on the employer's IMSS-registered economic activity class (fracción de actividad económica), the frequency and severity of occupational accidents reported over the preceding year, and the magnitude of the established permanent disability or death benefits triggered. The ST-1 notification therefore directly affects the employer's future IMSS riesgos de trabajo premium through the SINIESTRALIDAD (accident rate) calculation under the RACERF.

The formal ST-1 filing generates a claim number (número de siniestro) in the IMSS Sistema de Prestaciones Económicas (SIPE), enabling the injured worker to access: immediate medical attention at the IMSS Unidad Médica Familiar (UMF) or Hospital General de Zona (HGZ) without co-payment; temporary disability benefits (subsidio por incapacidad temporal) of 100% of the SDI from the day following the accident under Article 58 fracción I LSS; permanent partial disability pension (pensión por incapacidad permanente parcial) calculated on the percentage of valuation loss under Article 58 fracción II LSS; permanent total disability pension (pensión por incapacidad permanente total) of 70% of SDI under Article 58 fracción III LSS; and survivors' benefits (pensiones de viudez, orfandad, y ascendientes) in case of work-related death under Articles 64 through 68 LSS.

The STPS (Secretaría del Trabajo y Previsión Social) also receives occupational accident data from IMSS and uses it to update workplace safety statistics, identify high-risk industries and regions for focused inspection programmes, and assess compliance with NOMs including NOM-030-STPS-2009 and NOM-005-STPS-1998. Employers with high siniestralidad (accident rates) are placed on priority inspection lists by the Dirección General de Inspección Federal del Trabajo, and a high ST-1 filing rate may trigger administrative investigations into the employer's NOM compliance.

When Do You Need a IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo)?

An IMSS Workplace Accident Notification ST-1 Mexico is required every time a registered worker suffers an occupational accident or develops a work-related disease while employed by a company registered with the IMSS. The obligation to file the ST-1 arises immediately upon the occurrence of the accident or upon the employer's knowledge of the occupational disease, with mandatory submission deadlines that differ based on whether the incident results in temporary or permanent disability.

For accidents causing temporary disability (incapacidad temporal), the employer must present the ST-1 at the IMSS subdelegación or clinica familiar on the same day of the accident or, at the latest, within 24 hours — any delay beyond this period may result in the IMSS treating the absence as a non-occupational illness, depriving the worker of the 100% SDI subsidy available for riesgos de trabajo and replacing it with the 60% subsidy for enfermedad general. Employers who fail to file the ST-1 promptly may face demands from workers for the 40% SDI difference as unpaid wages (salarios caídos).

For commuting accidents (accidentes in itinere under Article 42 fracción II LSS), occurring on the direct route between the worker's registered home and the workplace, the ST-1 must be filed within 24 hours of the employer's knowledge of the accident. The IMSS requires the employer to document that the accident occurred on the habitual route and while the worker was travelling for the purpose of work — deviation from the normal route may disqualify the incident as a riesgo de trabajo.

When an occupational accident results in a permanent disability (incapacidad permanente), the ST-1 must be filed immediately and supplemented with the ST-2 form (Dictamen de Incapacidad Permanente o Defunción — Riesgos de Trabajo) issued by the IMSS medical services following the worker's clinical evaluation. The employer's obligation to notify does not depend on whether the worker received timely IMSS medical attention — the obligation exists independently.

The ST-1 is also required when an employer suspects a worker has developed an occupational disease (enfermedad de trabajo under Article 43 LSS), even if the disease was not immediately apparent. In this case, the employer must file the ST-1 and refer the worker to the IMSS for diagnostic confirmation through the specialised occupational medicine unit (Unidad de Medicina del Trabajo). The filing timeline for occupational disease notification is within 3 business days of the employer receiving medical documentation supporting the occupational origin of the condition.

Employers engaged in high-risk activities under the RACERF — those classified in IMSS occupational risk class III, IV, or V (including construction, chemical manufacturing, mining, and metalworking) — face more rigorous ST-1 filing review by IMSS auditors and are more likely to be subject to on-site IMSS inspections following multiple accident notifications within a calendar year.

What to Include in Your IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo)

A properly completed IMSS Workplace Accident Notification ST-1 Mexico must include the following elements to trigger IMSS coverage, protect the worker's benefit rights, and satisfy the employer's legal obligations under the LSS and RACERF.

Employer Data: Full corporate name (razón social), RFC, IMSS Registro Patronal number, and registered address of the centro de trabajo where the accident occurred. The IMSS uses the Registro Patronal to locate the employer's siniestralidad file and to assess the impact of the ST-1 filing on the annual prima de riesgo de trabajo calculation under RACERF Article 72.

Worker Data: Full name, Número de Seguridad Social (NSS) assigned by IMSS, CURP, RFC, date of birth, sex, and job title (puesto de trabajo) of the injured worker. The NSS is the primary identifier used by IMSS to access the worker's full coverage history, SDI, and medical record. If the worker was not previously registered with IMSS (a violation of LSS Article 15), the employer must simultaneously file an Alta del Trabajador along with the ST-1.

Accident Description and Classification: A detailed factual narrative of how the accident occurred, including: the date, time, and exact location of the accident within the workplace (área de trabajo); the activity the worker was performing at the time (what machine, tool, substance, or condition was involved); the type of injury (fracture, burn, laceration, contusion, amputation, etc.); and the injured body part. The IMSS medical reviewer uses this description to classify the accident as a riesgo de trabajo and to assess the severity for disability rating purposes under the LSS Valuación de Incapacidades table.

Accident Type Classification: The ST-1 must specify whether the accident was: an accidente de trabajo proper (occurring during work hours at the workplace); an accidente in itinere (occurring on the direct commuting route); a relapse (recaída) of a prior occupational injury; or an occupational disease (enfermedad de trabajo). This classification determines the applicable IMSS benefit formula and the RACERF siniestralidad calculation category.

Immediate Medical Attention Record: Documentation of the immediate first aid or emergency medical attention provided, including whether the worker was referred to the nearest IMSS UMF or Hospital General de Zona, and the name and IMSS registration number of the treating physician if the employer's own medical services were involved. Under Article 19 RACERF, employers with 100 or more workers must maintain an on-site first aid station staffed by certified personnel — the ST-1 notes whether employer first-aid services were utilised.

Witness Information: Name, job title, and signature of any workers who witnessed the accident. While witness information is not strictly required for the ST-1 to be accepted by IMSS, the presence of witness attestations strengthens the employer's documentation against potential challenges to the riesgo de trabajo classification, particularly for in itinere accidents or those with disputed circumstances.

Safety Officer Signature and Employer Certification: Signature of the employer or authorised representative certifying the accuracy of the accident description, and the signature of the company's safety officer (técnico en seguridad e higiene) if one is designated under the employer's NOM-030-STPS-2009 occupational safety programme. The employer's certification is subject to potential criminal liability for false declarations under Articles 247 and 311 of the Código Penal Federal.

Forms-legal.com provides this IMSS Workplace Accident Notification ST-1 Mexico template as a reference document. The actual ST-1 must be submitted through the IMSS IDSE (IMSS desde su Empresa) portal or presented in person at the relevant IMSS subdelegación. Employers should consult a licenciado en derecho laboral familiar with IMSS occupational risk regulations to ensure timely and accurate filing.

Cite this page

Reference this free template in an article, syllabus, or research note:

APA

Forms Legal. (2026). IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo) (Mexico) [Legal document template]. Forms Legal. https://forms-legal.com/mexico/government/declarations/imss-workplace-accident-notification-st1-mexico

MLA

"IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo) (Mexico)." Forms Legal, 2026, https://forms-legal.com/mexico/government/declarations/imss-workplace-accident-notification-st1-mexico.

BibTeX
@misc{formslegal-imss-workplace-accident-notification-st1-mexico,
  author       = {{Forms Legal}},
  title        = {IMSS Workplace Accident Notification ST-1 Mexico (Aviso de Accidente de Trabajo) (Mexico)},
  year         = {2026},
  howpublished = {\url{https://forms-legal.com/mexico/government/declarations/imss-workplace-accident-notification-st1-mexico}},
  note         = {Free legal document template}
}

Frequently Asked Questions

Statute-referenced template — Template last modified June 2026

This template is provided for informational purposes only and does not constitute legal advice. Laws vary by jurisdiction and change over time. Consult a qualified attorney for advice specific to your situation.Full disclaimer

Found an error? Let us know

Related Documents

You may also find these documents useful:

Reporte de Accidente de Trabajo México (LFT art. 504 / LSS art. 58)

Reporte de Accidente de Trabajo para México — conforme a la Ley Federal del Trabajo art. 504 y la Ley del Seguro Social art. 58. Incluye notificación al IMSS (formulario ST-7), análisis de causa raíz y plan de acciones correctivas exigidos por NOM-021-STPS-1994 e inspección de la STPS.

Formulario de Registro de Empresa ante la STPS México

Formulario de Registro de Empresa ante la STPS en México — conforme al artículo 15 de la Ley Federal del Trabajo y el Reglamento General de Seguridad e Higiene en el Trabajo — para registrar los centros de trabajo ante la Secretaría del Trabajo y Previsión Social con fines de inspección laboral y cumplimiento en materia de seguridad e higiene.

Aviso de Baja de Trabajador ante el IMSS México (Ley del Seguro Social art. 15)

Aviso de Baja de Trabajador ante el IMSS para México — conforme al Artículo 15, Fracción I de la Ley del Seguro Social. Notifica al IMSS la terminación de la relación laboral, detiene las cuotas obrero-patronales y cumple con el plazo legal de cinco días hábiles del artículo 15 LSS.

Programa de Seguridad y Salud en el Trabajo en México (NOM-030-STPS-2009)

Un Programa de Seguridad y Salud en el Trabajo para México — que establece el marco anual de gestión de seguridad del patrón conforme al artículo 509 de la Ley Federal del Trabajo, la NOM-030-STPS-2009 (servicios preventivos y programas de seguridad) y los requisitos de inspección de la STPS para la Comisión Mixta de Seguridad e Higiene.

Contrato de Trabajo por Tiempo Determinado México

Contrato de Trabajo por Tiempo Determinado para México — regido por el artículo 37 de la Ley Federal del Trabajo, aplicable cuando la naturaleza del trabajo requiere un plazo definido, como sustitución temporal, trabajo por proyecto o demanda estacional, con prestaciones obligatorias de IMSS, INFONAVIT, aguinaldo, prima vacacional y PTU.