If your payroll includes commissions, bonuses, overtime that counts toward the base, or Sunday premium, the contribution base salary (SBC, salario base de cotización) of those employees does not stay put. Every two months it is updated with what the employee actually earned in the previous two-month period. Here is how to do it without getting lost.
First, identify the salary type
| Salary type | How the SBC is obtained |
|---|---|
| Fixed | Daily salary × integration factor |
| Variable | Variable earnings from the previous two months ÷ days |
| Mixed | Integrated fixed part + variable part from the previous two months |
Step by step for the variable part
- Add up all variable earnings that count toward the base and that you paid in the previous two-month period.
- Divide that total by the days in the period or, if that is your company's practice, by the days of salary earned.
- Add the result to the integrated fixed part.
- Check the limits: it cannot be below the integrated minimum wage or above the 25 UMA cap (the UMA is the official reference unit used for these limits).
Deadlines
You have the first five business days of the month after each two-month period to file the update with IMSS (Mexico's Social Security Institute). Those months are January, March, May, July, September and November. The new salary takes effect from day 1 of that same month.
Watch out for
- Including items that should not count, such as PTU (mandatory profit sharing) or receipted travel expenses.
- Leaving out the part of punctuality and attendance bonuses that exceeds 10 % of the SBC.
- Filing late, which creates differences with the IMSS billing statement.
Legal basis
- Social Security Law, articles 27, 30 and 34, clauses II and III.
To check which items count and which do not, see what makes up the contribution base salary under article 27.
In Nomikhor the bimonthly variable salary is calculated automatically from what was paid in the period, respecting the minimum and the cap, and you can send the updates through the IDSE connection (the IMSS online filing system).