13(1)An officer of Revenue and Customs may enquire into a return under paragraph 8 or 9 if the officer gives notice that the officer intends to do so (a “notice of enquiry”) to the person whose return it is (“the taxpayer”).
(2)The normal rule is that a notice of enquiry may only be given up to the end of the period of twelve months after the day on which the return was delivered.
(3)But if the taxpayer has amended the return under paragraph 11(1), a notice of enquiry may be given up to the end of the period of twelve months after the amendment was made.
(4)A return which has been the subject of one notice of enquiry may not be the subject of another.
(5)An enquiry extends to anything contained in the return, or required to be contained in the return, subject to the following limitations.
(6)Where a notice of enquiry is given as a result of an amendment of the return under paragraph 11(1) and that notice is given—
(a)after the end of the period referred to in sub-paragraph (2), or
(b)after a closure notice has been issued in relation to an enquiry into the return,
the enquiry into the return is limited to matters to which the amendment relates or which are affected by the amendment.