Seventy-two questions. That is the length of the questionnaire in Reference Guide III of NOM-035-STPS-2018, the psychosocial risk standard issued by the STPS, Mexico's federal labor ministry. A site with 30 workers can use a 46-question version, and a site with 12 workers needs no psychosocial risk questionnaire at all. NOM-035 compliance is built on that ladder, and the rung your plant stands on depends on how many people work at that specific site, whatever the size of the group behind it in the US, Germany, Japan or Korea.
NOM-035 compliance is counted per work center
Section 2 of the standard sets three tiers by the number of people working at each "centro de trabajo", or work center: the place where production, storage, sales or services happen with people under an employment relationship (4.4).
Headcount is measured site by site, so one legal entity can sit in different tiers at different locations. A 300-person plant in the San Luis Potosí industrial zone and a 30-person warehouse in Villa de Reyes under the same company each follow their own list.
For scale: San Luis Potosí has 448 manufacturing plants with 51 or more employees (INEGI, Mexico's national statistics institute, DENUE business directory, May 2026). Every one of them falls in the top tier.
| Obligation (section) | Up to 15 | 16 to 50 | Over 50 |
|---|---|---|---|
| Written prevention policy, communicated (5.1) | Yes | Yes | Yes |
| Prevention measures and confidential complaint channel (8.1, 8.2) | Yes | Yes | Yes |
| Identify and refer workers after a severe traumatic event (5.5) | Yes | Yes | Yes |
| Psychosocial risk factor assessment (7.1, 7.2) | No | Yes, all workers | Yes, sample allowed |
| Organizational environment assessment (7.3) | No | No | Yes |
| Written report, records, control program when needed (7.7, 5.8, 8.4) | No | Yes | Yes |
| Repeat the assessment (7.9) | n/a | At least every 2 years | At least every 2 years |
Source: NOM-035-STPS-2018, section 2, Diario Oficial de la Federación (DOF, Mexico's Official Gazette), October 23, 2018.
What does a site with 15 or fewer workers need?
A written policy (5.1) covering three commitments: preventing psychosocial risk factors, preventing workplace violence and promoting a favorable organizational environment. Reference Guide IV includes a sample policy. The conformity procedure accepts brochures, newsletters or posters as proof the policy was communicated.
The site also needs the prevention measures in sections 8.1 and 8.2, including a safe, confidential way to file complaints and report violence. If a worker goes through a severe traumatic event on the job, such as a fatal accident or an armed robbery, the employer must identify that person and refer them to the IMSS (Mexican Social Security Institute), a private provider or the company doctor (5.5).
Sites with 16 to 50 workers: survey everyone
From 16 workers up, the site must identify and analyze psychosocial risk factors, and section 7.1(a) requires including every worker, with no sampling. Section 7.2 lists the factors: workplace conditions, workload, lack of control over the work, working hours and shift rotation, work-family interference, negative leadership and relationships, and workplace violence. Reference Guide II covers them in 46 questions.
Results go into a written report (7.7) that workers can consult (7.8). If the results call for controls, the site runs a program with actions, dates and a named owner (8.4).
What changes when a site has more than 50 workers?
Two things. First, the site adds an assessment of the organizational environment (7.3): sense of belonging, training for the job, clear responsibilities, participation and communication, workload distribution with regular hours, and performance review and recognition. Reference Guide III covers risk factors and environment together in 72 questions.
Second, the site may survey a random sample instead of everyone. Guide III gives the formula: n = 0.9604N / (0.0025(N - 1) + 0.9604). The standard's own example is 100 workers, which gives a sample of 80. For a 300-worker plant the same formula gives 169 (our calculation). The draw must include every shift and area and mirror the plant's gender split.
Sampling cuts the number of questionnaires, but the report, the control program and the communication of results stay at full scope.
Can a global engagement survey replace Guide III?
Usually not as-is. All five reference guides state that they are a complement to the standard and are not mandatory, and section 7.4 allows any method with defined questionnaires, scoring and risk levels. The catch is section 7.5: a questionnaire other than Guides II and III must be validated with workers at sites in Mexico, with at least ten respondents per item, Cronbach's alpha above 0.7, correlations with r above 0.5 and a confirmatory factor analysis that meets fit thresholds.
Most corporate engagement surveys were built for a different purpose. Unless your vendor can document that validation for Mexican workers, the survey is hard to defend as your NOM-035 method during an inspection.
Running the official guide in Spanish alongside your global survey is the lower-risk path, because using Guide III counts as meeting the method requirements in sections 7.1 to 7.5.
One more link to Mexican rules: section 7.6 requires the results to feed the safety and health diagnosis under NOM-030-STPS-2009, the document your safety officer under Mexico's NOM-030 is responsible for.
Training, records and fines: what the STPS checks
NOM-035-STPS-2018 does not require a DC-3, the official Mexican training record. It requires communicating information to workers (5.7) and training actions: section 8.2 asks for training and awareness for directors, managers and supervisors, training for whoever handles workplace violence cases, and a training needs assessment at least every two years. A course with attendance records can serve as evidence of those actions.
What an inspector looks for is documentary proof of the full cycle, from the written policy to the follow-up of the control program. Hiring an accredited verification unit is optional (9.1), and its report stays valid for two years if conditions do not change (9.4).
Breaches of safety and health standards carry fines of 250 to 5,000 UMA, the daily unit Mexico uses to set fines: MXN 29,327.50 to MXN 586,550 with the 2026 UMA of MXN 117.31, applied per affected worker (Federal Labor Law, arts. 992 and 994, section V). Our guide to STPS fines in Mexico explains how they add up. SIISA Consultores handles NOM-035 implementation through STPS compliance consulting for plants in San Luis Potosí, Villa de Reyes, Soledad and the industrial zone.
Frequently asked questions
Is NOM-035 mandatory for small sites?
Yes. NOM-035-STPS-2018 applies to every work center in Mexico, and sites with up to 15 workers must have a written policy, communicate it, apply prevention measures and offer a complaint channel. They are not required to run the psychosocial risk questionnaire.
What does a plant with more than 50 workers have to do for NOM-035?
It must assess psychosocial risk factors and the organizational environment, either with every worker or with a statistical sample, document the results in a report and run a control program when the results call for one. It also keeps records, communicates results to workers and repeats the assessment at least every two years.
Does NOM-035 training require a DC-3 certificate?
No. The standard requires communicating information and carrying out training actions, especially for managers and supervisors, but it does not require a DC-3. Attendance records from a course can show the training took place.
How does a 300-worker plant comply with NOM-035?
It can apply the Reference Guide III questionnaire to a random sample of 169 workers, which is what the guide's formula gives for 300 people, spread across shifts, areas and genders. The results go into a written report, feed the NOM-030-STPS-2009 safety and health diagnosis and, if the risk level requires it, a control program.
