The work-risk insurance premium directly affects employer contributions and is updated with each company's accident rate. The determination filed in February 2026 considered the work risks concluded between January 1 and December 31, 2025, regardless of when they began, plus the relapses and reassessments that must be incorporated under the regulations. Its result generally applies from March 2026. More than filling in a formula at year-end, compliance requires managing the notices, disabilities, relapses, medical opinions and closing dates of each risk throughout the year.
Who files and which period is reviewed
Employers review their accident rate annually and file the determination during February. To make up the review period they must consider the work risks concluded during the immediately preceding calendar year, regardless of the date on which they began. When the average number of workers is fewer than ten, the employer may choose to file the determination or pay the average premium for its class, under Article 72 of the Social Security Law. Changes of activity, class, fraction, substitution or employer registration must also be analyzed, because they can alter the treatment. Accidents in transit between home and work or vice versa are not counted in the formula, but that exclusion requires the case to be correctly classified and documented.
The formula depends on complete records
The calculation incorporates subsidized days, permanent disabilities, deaths and the average number of exposed workers, with the variables of the Social Security Law and its regulations. As a general rule, the premium may increase or decrease by up to one percentage point relative to the prior year, within the legal limits of 0.5 and 15 percent. A difference in the registration date, closing, relapse or disability percentage can alter the result. That is why it is advisable to reconcile the ST-7, ST-2 and ST-3 forms and available medical opinions with payroll, absenteeism and the IMSS informational query, without assuming that the latter replaces the official documents.
What to do after February 2026
The company must verify that the premium applied in the filings and payments from March matches the determination filed, and keep the acknowledgment, calculation file and supporting documents for each case. If it detects an omitted risk, an incorrect classification or a difference with the IMSS, it should promptly assess the appropriate clarification or correction, rather than waiting until the following February. To prepare for 2027, it is advisable to close the 2026 cases monthly and request missing documentation from the Institute when the worker does not provide it. This summary is informational and does not replace the review of employer registrations, resolutions or specific accident-rate cases.
Key points
- The February 2026 determination was based on the risks concluded during 2025, even if they began earlier.
- Accidents in transit are not included in the premium calculation.
- The ordinary annual variation is limited to one percentage point, between 0.5 and 15 percent.
- Employers with an average of fewer than ten workers may have the option provided by Article 72.
What to review
- Reconcile risks, disabilities, relapses and medical opinions against payroll and absenteeism on a monthly basis.
- Verify that the premium applied from March matches the acknowledgment filed in February 2026.
- Start building now the file that will support the February 2027 determination.