The Institute for Social Insurance (Zavod za socijalno osiguranje – ZSO), as the liaison body of the Republic of Serbia, is responsible for the implementation of social security agreements, and in its activities directly and actively cooperates with institutions of the mandatory social insurance system in the country and coordinates the work of those institutions in the implementation of international agreements on social security (Republic Fund for Pension and Disability Insurance, Republic Health Insurance Fund, Social Insurance Fund for Military Personnel and the National Employ