4(1)An officer of Revenue and Customs may correct any obvious error or omission in a return.U.K.
(2)A correction under this paragraph—
(a)is made by notice to the chargeable person, and
(b)is regarded as effecting an amendment of the return.
(3)The reference in sub-paragraph (1) to an error includes, for instance, an arithmetical mistake or an error of principle.
(4)A correction under this paragraph must be made within the 9 months beginning with—
(a)the day on which the return was delivered, or
(b)if the correction is needed as a result of an amendment under paragraph 3, the day on which the amendment was made.
(5)A correction under this paragraph has no effect if the chargeable person—
(a)amends the return so as to reject the correction, or
(b)gives a notice rejecting the correction in the special period mentioned in sub-paragraph (6).
(6)A notice is given in the “special period” if it is given—
(a)after the end of the period within which the chargeable person may amend the return, but
(b)before the end of the 3 months beginning with the date of issue of the notice of correction.
(7)A notice under sub-paragraph (5)(b) must be given to HMRC.