(1) Section 865 of the Principal Act is amended -

(a) by inserting the following subsection after subsection (2):

"(2A) Where a chargeable person (within the meaning of Part 41A) makes a claim under subsection (2) for repayment of tax which, but for an error or mistake referred to in that subsection, would not have been due it shall not constitute a valid claim for the purposes of subsection (3) unless the return and self assessment for the period to which the claim relates is amended, in accordance with section 959V, to correct the error or mistake.

(2B) Where a chargeable person (within the meaning of section 950) makes a claim under subsection (2) for repayment of tax which, but for an error or mistake referred to in that subsection, would not have been due and the claim relates to an accounting period which commenced before 1 January 2013 or to a year of assessment before the year of assessment 2013 it shall not constitute a valid claim for the purposes of subsection (3) unless the person's return for the accounting period or year of assessment, as the case may be, to which the claim relates is amended in accordance with section 959V to correct the error or mistake, and for this purpose section 959V shall apply to such an amendment as if -

(a) subsections (2) and (4) of that section were deleted,

(b) references in that section to 'return and a self assessment', 'return and the self assessment' and 'return or self assessment' were references to 'return', and