a - contributions paid by the employer in the private sector and contributions deducted from the salaries of the insured working therefor shall be calculated within a Gregorian year on the basis of the salaries paid thereto on January of every year.

b - The contributions of workers undertaking services in the private sector after January shall be calculated based on the salary of the month during which they have undertook the service, and such until the following January, after which they are treated based on the provisions of the preceding paragraph. contributions shall be calculated in full for the month in which the service starts, and shall not be due for the part of month in which the service is terminated.

c - contributions paid by the employer in the Governmental Sector, and contributions deducted from the salaries of the insured shall be calculated based on the monthly salary.