14.—(1) If a taxable person discovers an error in an MGD return which has resulted in that person’s liability to MGD being understated, and not more than four years has elapsed since the date that the return was due, the amount of the understatement may be included on the next MGD return in the manner prescribed if it—
(a)does not exceed £10,000; or
(b)does not exceed £50,000, and will not exceed 1% of the total net takings from dutiable machine games in the accounting period during which the understatement was discovered.
(2) Where a taxable person has made an error—
(a)in accounting for MGD; or
(b)in any return,
then, unless the error is corrected in accordance with paragraph (1), it must be corrected in such manner and within such time as the Commissioners may prescribe.