Where the appropriate assessing authority is satisfied, that a dealer is liable to pay interest under sub-section (1) of section 33 in respect of any period for default in making full payment by the prescribed date, of net tax according to the return furnished for that period, such authority shall determine under sub-section (1) of section 50, the interest payable for such period at any time after furnishing of such return but not later than the date of assessment under section 45, or section 46, or section 48, as the case may be.

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 (1) 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 within the time specified in this rule.