No property of any kind in this State shall ever be assessed for ad valorem taxes at a greater value than its fair cash market value nor shall any Board of Equalization of any governmental or political subdivision or taxing district within this State fix the value of any property for tax purposes at more than its fair cash market value; provided that in order to encourage the prompt payment of taxes, the Legislature shall have the power to provide that the taxpayer shall be allowed by the State and all governmental and political subdivisions and taxing districts of the State a three per cent (3%) discount on ad valorem taxes due the State or due any governmental or political subdivision or taxing district of the State if such taxes are paid ninety (90) days before the date when they would otherwise become delinquent; and the taxpayer shall be allowed a two per cent (2%) discount on said taxes if paid sixty (60) days before said taxes would become delinquent; and the taxpayer shall be allowed a one per cent (1%) discount if said taxes are paid thirty (30) days before they would otherwise become delinquent. The Legislature shall pass necessary laws for the proper administration of this Section.