Assessments or amended assessments to be final
20. Where no valid appeal has been lodged within the time specified in this Act again t an assessment in respect of the turnover tax, or where the amount of such tax has been determined on appeal, the assessments as made, or reduced, or increased or confirmed on appeal, as the ca e may be, shall be final and conclusive for all purposes of this Act as regards the amount of such tax: Provided that nothing in this Act shall prevent an Assessor from making an assessment or additional assessment for any quarter if it does not involve reopening any matter which has been determined on appeal for that quarter. |