“61 Deductions on account of tax from contract payments (1) On making a contract payment the contractor (see section 57(3)) must deduct from it a sum equal to the relevant percentage of so much of the payment as is not shown to represent the direct cost to any other person of materials used or to be used in carrying out the construction operations to which the contract under which the payment is to be made relates. (2) In subsection (1) “the relevant percentage” means such percentage as the Treasury may by order determine. … 62 Treatment of sums deducted (1) A sum deducted under section 61 from a payment made by a contractor— (a) must be paid to the Board of Inland Revenue, and (b) is to be treated for the purposes of income tax or, as the case may be, corporation tax as not diminishing the amount of the payment. (2) If the sub-contractor is not a company a sum deducted under section 61 and paid to the Board is to be treated as being income tax paid in respect of the sub- contractor’s relevant profits. (3) If the sum is more than sufficient to discharge his liability to income tax in respect of those profits, so much of the excess as is required to discharge any liability of his for Class 4 contributions is to be treated as being Class 4 contributions paid in respect of those profits. …”
“(1) Subject to subsection (2) below, the difference between-- (a) the amount of income tax and capital gains tax contained in a person's self-assessment under section 9 of this Act for any year of assessment, and (b) the aggregate of any payments on account made by him in respect of that year (whether under section 59A of this Act or otherwise) and any income tax which in respect of that year has been deducted at source, shall be payable by him or (as the case may be) repayable to him as mentioned in subsection (3) or (4) below … … (4) … the difference shall be payable or repayable on or before the 31st January next following the year of assessment. (5) An amount of tax which is payable or repayable as a result of the amendment or correction of a self-assessment under— (a) section … 28A of this Act …, or (b) …, is payable (or repayable) on or before the day specified by the relevant provision of Schedule 3ZA to this Act. (7) In this section any reference to income tax deducted at source is a reference to income tax deducted or treated as deducted from any income or treated as paid on any income.”
“(6) If, on an appeal notified to the tribunal, the tribunal decides— (a) that, ... the appellant is overcharged by a self-assessment; (b) … ; or (c) that the appellant is overcharged by an assessment other than a self-assessment, the assessment or amounts shall be reduced accordingly, but otherwise the assessment or statement shall stand good. (7) If, on an appeal notified to the tribunal, the tribunal decides (a) that the appellant is undercharged to tax by a self-assessment (b) …; or (c) that the appellant is undercharged by an assessment other than a self-assessment, the assessment or amounts shall be increased accordingly. (7A) If, on an appeal notified to the tribunal, the tribunal decides that a claim or election which was the subject of a decision contained in a closure notice under section 28A of this Act should have been allowed or disallowed to an extent different from that specified in the notice, the claim or election shall be allowed or disallowed accordingly to the extent that the tribunal decides is appropriate, but otherwise the decision in the notice shall stand good. (8) Where, on an appeal notified to the tribunal against an assessment (other than a self-assessment) which— (a) assesses an amount which is chargeable to tax, and (b) charges tax on the amount assessed, the tribunal decides as mentioned in subsection (6) or (7) above, the tribunal may, unless the circumstances of the case otherwise require, reduce or, as the case may be, increase only the amount assessed; and where any appeal notified to the tribunal is so determined the tax charged by the assessment shall be taken to have been reduced or increased accordingly. …”
“Sections 31(1)(b) (that an appeal may be brought against the conclusion or amendment in a closure notice) and s 50(6) and (7) (that the appeal Commissioners’ jurisdiction is to determine whether the appellant is over- or undercharged by the self-assessment) [TMA] do not appear to fit together well. What, for example, is the procedure for an appeal against a conclusion that does not lead to an amendment? And if there is an appeal against both the conclusion and the amendment the appeal Commissioners are apparently not required to adjudicate on the reasons for the amendment; they must either reduce or increase the assessment or allow it to stand good.” and later in that paragraph: “Accordingly, I consider that s 50(6) (and similarly with (7)) should be read in the context of s 31(1)(b) in this way: If, on an appeal [against a conclusion or amendment to a self-assessment stated in a closure notice], it appears to the majority of the Commissioners present at the hearing, by examination of the appellant on oath or affirmation, or by other ...evidence,— (a) that, ...the appellant is overcharged by a[n amended] self-assessment [so far as concerns matters appealed against];… the assessment… shall be reduced accordingly, but otherwise the assessment …shall stand good.”
“ … every return under section 8 … of this Act shall include a self-assessment, that is to say-- (a) an assessment of the amounts in which, on the basis of the information contained in the return and taking into account any relief or allowance a claim for which is included in the return, the person making the return is chargeable to income tax and capital gains tax for the year of assessment; and (b) an assessment of the amount payable by him by way of income tax, that is to say, the difference between the amount in which he is assessed to income tax under paragraph (a) above and the aggregate amount of any income tax deducted at source … but nothing in this subsection shall enable a self-assessment to show as repayable any income tax treated as deducted or paid by virtue of [ irrelevant provisions ]…”
“In this section and sections 8A, 9 and 12AA of this Act, any reference to income tax deducted at source is a reference to income tax deducted or treated as deducted from any income or treated as paid on any income.”