(1) Subject to this section, the tax payable under an assessment shall, on the service of the notice of assessment on the person assessed, be due and payable at the place specified in that notice whether or not that person appeals against the assessment.

(2) Where the tax payable under an assessment is increased on appeal the additional tax payable by virtue of the increased assessment shall, on the service of the notice of the increased assessment on the person assessed, be due and payable at the place specified in that notice.

(3) Where any tax is payable in accordance with subsection (1) or (2) the Director General may allow the tax to be paid by instalments in such amounts and on such dates as he may determine.

(4) Subject to subsection (3), where any tax due and payable on the service of a notice in accordance with subsection (1) or (2) has not been paid within thirty days after the service of that notice (or within such longer period as may be allowed by the Director General), so much of the tax as is unpaid upon the expiration of those days or that period, as the case may be, shall without any further notice being served on him be increased by a sum equal to ten per cent of the tax so unpaid, and that sum shall be recoverable as if it were tax due and payable under this Act:

Provided that-

(a) if the tax payable is reduced on appeal or otherwise the sum paid or payable by way of increase shall be reduced proportionately; and

(b) the Director General may in his discretion for any good cause shown remit the whole or any part of any increase in the tax payable under this subsection.