599 In the present case if we construe the words "on the basis of return" occurring in sub section (2) of section 7 of the Act as on the basis of a true and proper return which ought to have been filed under sub section (1) of section 7 then all the three classes of persons viz. (i) those who have not filed any return at all and who are later on found to be liable to be assessed, (ii) those who have filed a true return but have not deposited the full amount of tax which they are liable to pay and (iii) those who have filed a return making a wrong claim that either the whole or any part of the turnover is nat taxable and who are subsequently found to have made a wrong claim, would be placed in the same position and they would all be liable to ply interest on the amount of tax which they are liable to pay but have not paid as required by sub section (2) of section 7 of the Act.