Where the appropriate assessing authority is satisfied-

(a) that a dealer has failed to furnish a return under section 32, in respect of any period before the assessment under section 45 or section 46 or section 48 for such period, and

(b) on completion of such assessment, that the said dealer has not paid full amount of net tax payable for such period by the prescribed date for furnishing the return,

and is liable to pay interest under sub-section(2) of section 33, in respect of such period, such authority shall determine under sub-section (1) of section 50 the interest payable at the time of assessment under section 45 or section 46 or section 48 as the case may be, for such period.

Provided that where the appropriate auditing authority is required to make assessment of net tax under sub-section (1) of section 46 in respect of any year or part of a year, such authority shall, notwithstanding the provisions of this rule, where he is satisfied that the dealer is liable to pay interest under sub-section (2) of section 33 in respect of any period falling within such year or part of such year, determine under this rule interest in respect of such period at the time specified in this rule.