Provided that before levying any such penalty, the assessee shall be given a reasonable opportunity of being heard :
Provided further that where the assessee proves to the satisfaction of the Assessing Officer that the default was for good and sufficient reasons, no penalty shall be levied under this section.
Explanation.—For the removal of doubt, it is hereby declared that an assessee shall not cease to be liable to any penalty under this sub-section merely by reason of the fact that before the levy of such penalty he has paid the tax.
(2) Where as a result of any final order the amount of tax, with respect to the default in the payment of which the penalty was levied, has been wholly reduced, the penalty levied shall be cancelled and the amount of penalty paid shall be refunded.