[5 -(1) An officer of the Board may enquire into –
(a) a claim made by any person, or
(b) any amendment made by any person of a claim made by him, if, before the end of the period mentioned in sub-paragraph (2) below, he gives notice in writing of his intention to do so to that person or, in the case of a partnership claim, any successor of that person.
[(2) The period referred to in sub-paragraph (1) above is whichever of the following ends the latest, namely –
(a) the period ending with the quarter day next following the first anniversary of the day on which the claim or amendment was made;
(b) where the claim or amendment relates to a year of assessment, the period ending with the first anniversary of the 31st January next following that year; and
(c) where the claim or amendment relates to a period other than a year of assessment, the period ending with the first anniversary of the end of that period;
and the quarter days for the purposes of this sub-paragraph are 31st January, 30th April, 31st July and 31st October.
(3) A claim or amendment which has been enquired into under sub-paragraph (1) above shall not be the subject of –
(a) a further notice under that sub-paragraph; or
(b) if it is subsequently included in a return, a notice under [section 9A(1) or 12AC(1) of this Act or paragraph 24 of Schedule 18 to the Finance Act 1998]3.]2]1