New Circular couldn't be used to demand tax for prior period if first Circular had provided exemptio

CST & VAT : Karnataka VAT : Where first clarification dated 3-6-2006 had provided that 'white oats were exempt' and subsequent clarification dated 20-1-2010 provided that 'white oats were taxable', said subsequent clarification would be effective only from 20-1-2010 and no demand can be raised prior to said date