(I B) No appeal against an assessment order under this Act shall be entertained unless the appellant has furnished satisfactory proof of the payment of not less than (a) the amount of tax or fee due under this Act on the turnover of sales or purchases, as the case may be, admitted by the appellant in the returns filed by him or at any stage in any proceedings under this Act, whichever is greater, where all the returns for the assessment year have been filed, or (b) the amount of tax or fee due under this Act on the turnover of sales or purchases, as the case may be, admitted by the appellant in the returns, if any, filed by him or at any stage in any proceedings under this Act, or twenty per cent, of the amount of tax or fee assessed, whichever is greater, where some of the returns for the assessment year have not been filed or no return has been filed for such year: 1037 Provided that the Appellate Authority may, for special and adequate reason to be recorded in writing, waive or relax the requirement of the Clause (b) of this sub section in so far as it relates to deposit of twenty per cent of the amount of tax or fee assessed.