(a)If the Commissioner is not satisfied that the returns furnished in respect of any period are correct and complete and he thinks it necessary to require the presence of the dealer or the production of further evidence, he shall serve on such dealer in the prescribed manner a notice requiring him on a date and at a place specified therein either to attend and produce or cause to be produced all evidence on which such dealer relies in support of his returns, or to produce such evidence as is specified in the notice.