(1)Where—
(a)the author of a literary, dramatic, musical or artistic work assigns the copyright therein wholly or partially or grants any interest in the copyright by licence ; and
(b)the consideration for the assignment or grant consists wholly or partially of a lump sum payment the whole amount of which would, but for this section, be included in computing the amount of his profits or gains for a single year of assessment; and
(c)the author was engaged on the making of the work for a period of more than twelve months,
he shall be entitled to claim that effect shall be given to the subsequent provisions of this section in connection with that payment.
(2)If the period for which he was engaged on the making of the work does not exceed twenty-four months, then, for all the purposes of the Income Tax Acts, one half only of the amount of the payment shall be treated as having become receivable on the date on which it actually became receivable, and the remaining half shall be treated as having become receivable twelve months before that date.
(3)If the period for which he was engaged on the making of the work exceeds twenty-four months, then, for all the purposes of the Income Tax Acts, one third only of the amount of the payment shall be treated as having become receivable on the date on which it actually became receivable, and one third shall be treated as having become receivable twelve months, and one third twenty-four months, before that date.
(4)A claim under subsection (1) of this section must be made to the Commissioners of Inland Revenue not later than twelve months from the end of the year of assessment mentioned in that subsection, and section nineteen of the [15 & 16 Geo. 5. c. 36.] Finance Act, 1925 (which relates to the making and allowing of claims for certain reliefs and to rights of appeal), shall apply in relation to claims under the said subsection (1) as it applies in relation to the claims mentioned in that section.
(5)Where, on a claim made under this section, liability to tax falls to be adjusted in accordance with subsection (2) or subsection (3) of this section, such additional assessments, reductions of assessments and repayments shall be made as are necessary to give effect to the provisions of this section.
(6)In this section, the expression " author " includes a joint author, and the expression " lump sum payment " includes an advance on account of royalties which is not returnable.