18(1)A person who—
(a)by virtue of subsection (3), (7) or (9) of section 57 of this Act becomes subject to a duty to take action as mentioned in subsection (4) of that section, and
(b)fails to take action as so mentioned,
shall be liable to a penalty of £10,000; but this is subject to sub-paragraph (2) below.
(2)A failure falling within sub-paragraph (1) above shall not give rise to liability to a penalty under this paragraph if the person concerned satisfies the Commissioners or, on appeal, an appeal tribunal that there is a reasonable excuse for the failure.
(3)If it appears to the Treasury that there has been a change in the value of money since the passing of this Act or, as the case may be, the last occasion when the power conferred by this sub-paragraph was exercised, they may by order substitute for the sum for the time being specified in sub-paragraph (1) above such other sum as appears to them to be justified by the change.
(4)An order under sub-paragraph (3) above shall not apply in relation to a case where the duty mentioned in sub-paragraph (1) above was imposed before the date on which the order comes into force.