Every month and every two months you have to pay IMSS (Mexico's Social Security Institute) the so-called employer-employee contributions, or cuotas obrero-patronales. They fund the mandatory insurance branches, retirement savings and worker housing. All of them start from two figures: the contribution base salary (SBC, salario base de cotización) and the days contributed. Part is paid by the company and part is withheld from the employee's pay slip.
2026 rates, branch by branch
| Insurance branch | Calculation base | Employer | Employee | Frequency |
|---|---|---|---|---|
| Sickness and maternity: fixed fee | UMA | 20.40 % | — | Monthly |
| Sickness and maternity: excess over 3 UMA | SBC − 3 UMA | 1.10 % | 0.40 % | Monthly |
| Cash benefits | SBC | 0.70 % | 0.25 % | Monthly |
| Pensioners' medical expenses | SBC | 1.05 % | 0.375 % | Monthly |
| Occupational risk | SBC | Company's risk premium | — | Monthly |
| Disability and life | SBC | 1.75 % | 0.625 % | Monthly |
| Childcare and social benefits | SBC | 1.00 % | — | Monthly |
| Retirement | SBC | 2.00 % | — | Bimonthly |
| Old-age and severance at advanced age (CEAV) | SBC | 3.150 % to 7.513 % | 1.125 % | Bimonthly |
| Infonavit (housing fund) | SBC | 5.00 % | — | Bimonthly |
The UMA (Unidad de Medida y Actualización) is the official reference unit used instead of the minimum wage for these calculations.
Two rules to keep in mind
- Cap: the SBC cannot exceed 25 UMA, which in 2026 is $2,932.75 per day.
- Minimum wage: when the employee earns the minimum wage, the employer also pays the employee's share.
Step by step: an employee with a $500 SBC for 30 days
Assume a risk premium of 0.54355 % and a month with no sick leave and no absences. The result is:
| Item | Employer | Employee |
|---|---|---|
| Fixed fee | $717.94 | — |
| Excess over 3 UMA | $48.86 | $17.77 |
| Cash benefits | $105.00 | $37.50 |
| Pensioners' medical expenses | $157.50 | $56.25 |
| Occupational risk | $81.53 | — |
| Disability and life | $262.50 | $93.75 |
| Childcare | $150.00 | — |
| Retirement | $300.00 | — |
| Old-age and severance (CEAV) | $1,126.95 | $168.75 |
| Infonavit | $750.00 | — |
| Total | $3,700.28 | $374.02 |
Note: retirement, CEAV and Infonavit are shown for 30 days only so you can compare; in practice they are paid every two months.
Watch out: days contributed
Not every branch subtracts the same days. Keep this in mind when you check your figures:
- Sickness and maternity: sick-leave days are subtracted.
- Occupational risk, disability and life, childcare and CEAV: both sick-leave days and absences are subtracted.
- Retirement and Infonavit: only absences are subtracted.
Absences also have a limit: at most seven per month are subtracted.
Legal basis
- Social Security Law (LSS), articles 25, 27, 28, 31, 36, 39, 71, 106, 107, 147, 168 and 211.
- Infonavit Law, article 29 (5 % employer contribution).
- Amendment to the Social Security Law published in the Official Gazette (DOF) on December 16, 2020, fourth transitory article (CEAV).
To see how the CEAV rate rises every year, read how much the employer CEAV contribution increases in 2026.
In Nomikhor, IMSS contributions are calculated automatically with up-to-date rates, UMA and minimum wages. You can download the EMA and EBA, run the Nomikhor–SUA–IDSE reconciliation to catch differences before paying, and export to SUA (the IMSS payment software) without retyping anything.