Tom Klukowski
Fyware Partner · Valcre Marketing
How can we help?
How the IMSS risk premium is calculated
Article 72 of the Social Security Law sets one formula for every company, and each plant fills it in with its own accident record for the year.
Premium = [(S/365) + V × (I + D)] × (F/N) + M
- S
- Subsidized days of temporary disability: the disability days from the work injuries and illnesses closed during the year, including relapses.
- I
- Sum of the percentages of permanent disabilities, partial and total, divided by 100. It comes from the ST-3 rulings; if a reassessment is ruled in a later year, only the difference counts.
- D
- Number of work-related deaths.
- N
- Average workers exposed to risk: the contribution days of all workers during the year, divided by 365 (RACERF art. 36).
- V = 28
- Average length of working life, in years. That is why a death or a total permanent disability weighs so much.
- F = 2.3
- Premium factor. It is 2.2 if the workplace has an occupational safety management system accredited by Mexico's Labor Ministry (STPS).
- M = 0.005
- Minimum risk premium, added at the end.
The result is multiplied by 100 and rounded to five decimals: that is the premium as a percentage. This calculator does the math at full precision and rounds once, at the end, which is how the example in the 2026 IMSS user manual comes out (104.04841%). The instructions for form CLEM-22 ask you to round each operation to eight decimals, and that can change the fifth decimal.
What the law says about the change from one year to the next
- One point at most. The premium can only go up or down “in a proportion no greater than one percent” of last year's rate (LSS art. 74). In the official example of form CLEM-22A, a company paying 3.18550% calculates 0.91048% and its new premium is 2.18550%.
- Between 0.5% and 15%. No premium goes below 0.5% or above 15% (LSS art. 74). The formula can give more: in the 2026 IMSS user manual example it gives 104.04841%, and the new premium is last year's plus one point.
- New companies pay the class average premium. A company that registers or changes its activity pays the average premium of its class until it completes a calendar year (LSS art. 73): class I 0.54355%, II 1.13065%, III 2.59840%, IV 4.65325% and V 7.58875%.
- Fewer than 10 workers. They can file the determination or pay their class average premium (LSS art. 72, last paragraph). With exactly 10, filing is required.
- With no work injuries or illnesses, the premium drops one point a year until it reaches 0.5%. If you are already at 0.5% with no cases, IMSS states you are not required to file.
- F = 2.2 with accreditation. It applies with the STPS accreditation letter, validated every year, in the determination for the year after it was obtained (RACERF art. 39).
Sources: Social Security Law (Ley del Seguro Social, LSS), arts. 72 to 74 (amended in the Official Gazette of December 20, 2001; the 2026 amendment did not touch them); LSS Regulations on Registration, Classification of Companies, Collection and Audit (RACERF), arts. 32 to 39; IMSS forms CLEM-22 and CLEM-22A and their instructions; 2026 IMSS user manual and SUA/IDSE guide. Accessed October 20, 2026.
2027 determination calendar
January 1 to December 31, 2026
Work injuries and illnesses closed during the year count (medical release, permanent disability or death), no matter when they happened. A December accident whose disability runs into January counts the following year. Commuting accidents do not count (LSS art. 72).
During February 2027
The determination is filed; IMSS states February 1 to 28. Online, with the file SUA generates and your e.firma in IDSE; in person, with form CLEM-22 and, if there were cases, CLEM-22A.
March 1, 2027 to February 29, 2028
The new premium applies. If you had to file and did not, the fine ranges from 20 to 210 times the UMA (LSS arts. 304-A and 304-B), reduced by 20% if you pay within 15 business days of notice (RACERF art. 189).
Every accident that does not happen lowers your premium
In the formula, a death or a total permanent disability weighs as 28 years of working life, and every disability day adds to S. Apart from the accreditation that brings F down to 2.2, the only thing that moves the premium is the accident not happening. Fyware builds virtual reality simulators to practice high-risk procedures (fire extinguishers, forklifts, cranes, lockout/tagout) before touching the equipment.
See Fyware Safe
Frequently asked questions about the IMSS risk premium
How is the IMSS work risk premium calculated?
With the formula in article 72 of Mexico's Social Security Law: Premium = [(S/365) + 28 × (I + D)] × (F/N) + 0.005, where S is subsidized disability days, I the sum of permanent disability percentages divided by 100, D the number of deaths and N the average workers exposed to risk. The result is multiplied by 100 and rounded to five decimals. Then two rules from article 74 apply: the premium cannot change more than one point against last year's, and it stays between 0.5% and 15%.
When is the 2027 risk premium determination filed?
During February 2027; IMSS states February 1 to 28. It is calculated with the work injuries and illnesses closed from January 1 to December 31, 2026, and the new premium applies from March 1, 2027 to February 29, 2028 (RACERF art. 32).
Who has to file it?
Companies with 10 or more average workers. They do not have to file if the premium comes out the same as last year's, or if they are already at the 0.5% minimum with no cases during the year. Companies with fewer than 10 workers can file or pay their class average premium (LSS art. 72).
More questions
How much can my premium go up or down in a year?
One percentage point at most, up or down (LSS art. 74). If you paid 3.18550%, the new rate falls between 2.18550% and 4.18550% even if the formula gives something else. It also never goes below 0.5% or above 15%.
What happens if I do not file the determination?
If you were required to, the fine ranges from 20 to 210 times the UMA (LSS arts. 304-A, sec. XV, and 304-B, sec. III), reduced by 20% if you pay within 15 business days of notice (RACERF art. 189). There is no fine when the premium comes out the same as last year's.
What is the class average premium and when is it paid?
It is the premium article 73 of the LSS sets for each risk class: 0.54355% (class I), 1.13065% (II), 2.59840% (III), 4.65325% (IV) and 7.58875% (V). Companies that register or change their activity pay it until they complete a calendar year, and it is the prior premium in their first calculation.
Do commuting accidents count toward the premium?
No. Article 72 of the LSS excludes them: accidents while traveling from home to work or back do not count in the company's accident record. Relapses and reassessments of permanent disabilities do count (RACERF art. 37).
How accurate is this calculator?
It matches the four official IMSS examples to the fifth decimal: the two cases in the instructions for form CLEM-22A, the one in the 2026 user manual and the one in the 2026 SUA/IDSE guide. It does the math at full precision and rounds once at the end; the manual calculation on form CLEM-22, which rounds each operation to eight decimals, may differ in the fifth decimal. The official determination is the one SUA generates.
How do I lower my risk premium?
By lowering the accident record: fewer disability days, fewer permanent disabilities and no deaths. The premium drops one point a year at most, so the effect builds up. Accrediting an occupational safety management system lowers the factor from 2.3 to 2.2. Practicing high-risk procedures before touching the equipment, as in the Fyware Safe simulators, goes after the cause.
Let's talk about your plant
Tell us what you want to solve in your plant. Fyware designs extended reality around the equipment and constraints of your operation, and builds it to grow from a pilot to the whole site.
Tom Klukowski, Fyware Partner · Valcre Marketing We reply in under 24 business hours, with scope, timeline and investment range. In the meeting you see the simulator running and what it would take to bring it to your plant, with scenarios adapted to your layout. And if you need to sell it internally, this page is your presentation: share it with your team.
