Kindly refer proviso as per finance act Interest on delayed payment of tax. 50. (1) Every person who is liable to pay tax in accordance with the provisions of this Act or the rules made thereunder, but fails to pay the tax or any part thereof to the Government within the period prescribed, shall for the period for which the tax or any part thereof remains unpaid, pay, on his own, interest at such rate, not exceeding eighteen per cent., as may be notified by the Government on the recommendations of the Council. 1[Provided that the interest on tax payable in respect of supplies made during a tax period and declared in the return for the said period furnished after the due date in accordance with the 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, shall be levied on that portion of the tax that is paid by debiting the electronic cash ledger.]