Section 141B(2) in The Gujarat Provincial Municipal Corporations Act, 1949
(2)For the purpose of levy of tax on buildings in the City under sub-section (1) ,-(a)the buildings may be classified into residential buildings and buildings other than residential; and(b)the Corporation may determine one rate of tax for residential buildings and.the other rate of tax for buildings other than residential:Provided that it shall be lawful for the Corporation to determine for residential buildings, the carpet area of which does not exceed forty square metres, such rate of tax as is lower than the rate of tax determined for residential buildings generally under this sub-section.