As per Assam vat rule 22
The notice required to be served on the dealer as required under sub-section (1) of section 36 shall be in Form-20.
(a) a registered dealer is selected for audit assessment by the Prescribed Authority on the basis of any criteria or on random basis; or
(b) the Prescribed Authority is not satisfied with the correctness of any return filed under section 29; or bona fides of any claim of exemption, deduction, concession, input tax credit or genuineness of any declaration, evidence furnished by a registered dealer in support thereof; or
(c) the Prescribed Authority has reasons to believe that detailed scrutiny of the case is necessary; or
(d) a provisional assessment under section 34 has been made, the Prescribed Authority may, notwithstanding the fact that the dealer may already have been assessed under section 34 or section 35, serve on such dealer in the prescribed manner a notice requiring him to appear on a date and place specified therein, which may be in the business premises or at a place specified in the notice, to either attend and produce or cause to be produced the books of account and all evidence on which the dealer relies in support of his returns including tax invoice, if any, or to produce such evidence as specified in the notice. For this purpose, the Prescribed Authority may also undertake tax audit of stock-in-trade of the dealer.