The Commissioner or the Assessing authority or any other Tax Officer as the case may be shall, in each case, selected for audit assessment under Section 39 serve on the dealer a notice in Form VAT-17

[a] calling upon him to produce his books of accounts and other documents which such authority wishes to examine together with any objection which the dealer may wish to produce in support thereof; and

[b] stating the period in respect of which assessment is proposed and he shall fix a date ordinarily not less than 20 days after the issuance of the notice for producing such accounts and documents and for considering any objections which the dealer may prefer.

Provided that a dealer may be assessed on the basis of a single notice and by a single order of assessment involving more than one tax period covered by a return so long as all such tax period fall in one financial year.