(1)[F1The Commissioners F2...] must construct tax tables with a view to securing that so far as possible—

(a)the total income tax payable in respect of PAYE income for any tax year [F3and any relevant debts payable during that tax year are] deducted from PAYE income paid during that year, and

(b)the income tax [F4and any relevant debts] deductible or repayable on the occasion of any payment of, or on account of, PAYE income [F5are such] that the following proportions are the same—

(i)the proportion which the total net income tax [F6and any relevant debts] deducted since the beginning of the tax year bears to the total income tax [F7and the total amount of any relevant debts] payable for the year, and

(ii)the proportion which the part of the tax year which ends with the date of the payment bears to the whole year.

(2)References in subsection (1) to the total income tax payable for the year are to be read as references to the total income tax estimated to be payable for the year in respect of the income in question—

(a)subject to a provisional deduction for allowances and reliefs, and

[F8(b)subject to an adjustment in respect of amounts required to be deducted or repaid by PAYE regulations made under item 1A[F9, 2 [F10, 2ZA] or 2A] in the list in section 684(2).]

(3)For the purpose of estimating the total income tax payable as mentioned in subsection (1)(a), it may be assumed, in relation to any payment of, or on account of, PAYE income, that the following proportions will be the same—

(a)the proportion which the income paid in the part of the tax year which ends with the making of the payment bears to the income for the whole year, and

(b)the proportion which that part of the tax year bears to the whole year.

[F11(4)PAYE regulations may make provision, where it appears to [F12an officer of Revenue and Customs] that it is impracticable for a payer to deduct tax by reference to tax tables—

(a)for deductions to be made by the payer in accordance with other arrangements agreed as mentioned in section 684(7A)(a), or

(b)for the payee to be required to keep records and make payments and returns as if he were the payer.]