(1) Where on consideration of the report submitted by the Audit Officer under sub-rule (7) of Rule 21D the designated officer deems it necessary to proceed under sub-section (2), of section 18 he may authorise the audit officer or any other officer to proceed to reject the return submitted by the dealer and complete the assessment to the best of his judgment in accordance with these rules.

(2) Where the officer authorised under sub-rule (1) considers it necessary that a further verification of the accounts or other records is necessary, he shall serve upon the dealer a summons in Form No 50 specifying therein the details of the records to be made available, the date on which and the time and place at which the dealer has to make available the books of accounts or other records.

(3) On receipt of the summons in Form No. 50, the dealer or any other person assisting him in carrying on business, shall make available the books of accounts and other records, stock statements and goods as specified in the notice.

(4) (i) Where in an audit, any irregularity as specified under sub-section (2) of section 18 is detected and such irregularity relates to one return period only and does not disclose any pattern of suppression, the best judgment assessment shall be limited to the return period to which the irregularity relates.

(ii) Where the irregularity detected is the failure to prove the claim of any exemption or reduction in rate of tax, the best judgment assessment shall be limited to the disallowance of the claim of such exemption or reduction, as the case may be. Where any such claim of exemption or reduction in rate of tax is disallowed, in addition to the tax that becomes additionally payable, interest under sub-section (3) of section 23 and twice the interest as penalty shall be demanded or levied.

(iii) Where the irregularity relates to suppression of taxable turnover and a pattern of suppression is clearly made out, the best judgment assessment shall be in respect of all the return periods to which the pattern is applicable.

(iv) Where the best judgment assessment is done after the expiry of the year in which the relevant return periods fall, and the best judgment relates to more than one return period, the assessment shall be made by a single order. However assessment relating to return periods falling under different years shall not be made by a single order.

(v) The assessing authority making the best judgment assessment shall serve on the dealer a notice clearly specifying the irregularities or defects noticed and the manner in which the best judgment assessment is proposed to be completed. Where a pattern of suppression is detected, the pattern and the relation borne by such pattern of suppression to the estimate proposed shall be clearly made out in the notice.