(a) In the computation of a chargeable gain, consideration for the disposal shall be taken into account without any discount for postponement of the right to receive any part of the consideration and without regard to a risk of any part of the consideration being irrecoverable or to the right to receive any part of the consideration being contingent.
(b) Where any part of the consideration taken into account in accordance with paragraph (a) is shown to the satisfaction of the inspector to be irrecoverable, such adjustment, whether by means of discharge or repayment of tax or otherwise, shall be made as the case may require. Subsection (4) or (6) of section 865 shall not prevent the Revenue Commissioners from repaying an amount of tax as a consequence of any such adjustment.
(2) Subsection (1) shall apply for the purposes of corporation tax as it applies for the purposes of capital gains tax.