(1) In case, where the supplies made during a tax period are declared by the registered person in the return for the said period and the said return is furnished after the due date in accordance with provisions of section 39, except where such return is furnished after commencement of any proceedings under section 73 or section 74 in respect of the said period, the interest on tax payable in respect of such supplies shall be calculated on the portion of tax which is paid by debiting the electronic cash ledger, for the period of delay in filing the said return beyond the due date, at such rate as may be notified under sub-section (1) of section 50.

(2) In all other cases, where interest is payable in accordance with sub section (1) of section 50, the interest shall be calculated on the amount of tax which remains unpaid, for the period starting from the date on which such tax was due to be paid till the date such tax is paid, at such rate as may be notified under sub-section (1) of section 50.