(1) Where the prescribed authority upon    information received has reasons to believe that any enrolled person has paid    tax for any year at a rate lower than what is payable by such person, or such    person has not paid any tax for any year, under this Act, or such authority    has received application from any person for refund of any amount under    section 18, it may, after giving such person a reasonable opportunity of being    heard, determine, in the prescribed manner, the amount of tax, penalty or    interest payable by him.
(2) The amount of tax determined under    sub-section (1), less the sum, if any, already paid in respect of such year,    shall be paid by such persons on demand by the prescribed authority in the    prescribed manner.