Article 85 of Social Insurance Law

Contributions paid by the employer in the private and oil sectors—excluding wholly state-owned companies—and those deducted from the salaries of insured persons working for that employer during a year shall be calculated on the basis of the salary for January of each year. As for those who enter service in a month other than that month, their contributions shall be calculated on the basis of the salary for the month in which they entered service until the following first of January, after which they shall be treated on the basis set out in the preceding paragraph. The provision of the preceding paragraph shall apply to persons to whom this Law applies for the first time. Contributions shall be payable in full for the month in which service begins and shall not be payable for the part of the month in which service ends. In calculating the monthly salary of persons who are not paid monthly, the number of working days in a month shall be set at thirty days, except for persons who are not paid salaries for weekly rest days, for whom the number of working days in a month shall be set at twenty-six days.