Article 29 of the Mexican Social Security Law
The following rules shall apply to determine the form of contribution:
- The calendar month shall be the period for payment of installments;
- To fix the daily salary in case it is paid by week, fortnight or month, the corresponding remuneration will be divided by seven, fifteen or thirty respectively. The same procedure shall be used when the salary is fixed for periods other than those indicated; and
- If due to the nature or peculiarities of the work, the salary is not stipulated per week or per month, but per day worked and includes fewer days than those of a week or the insured person works reduced working days and his salary is determined per unit of time, in no case will contributions be received based on a salary lower than the minimum wage.