Where a royalty or other sum to which section 348 or 349(1) applies is paid in respect of the user of a patent, and that user extended over a period of six complete years or more, the person receiving the payment may on the making of a claim require that the income tax or corporation tax payable by him by reason of the receipt of that sum shall be reduced so as not to exceed the total amount of income tax or corporation tax which would have been payable by him if that royalty or sum had been paid in six equal instalments at yearly intervals, the last of which was paid on the date on which the payment was in fact made.

Subsection (1) above shall apply in relation to a royalty or other sum where the period of the user is two complete years or more but less than six complete years as it applies to the royalties and sums mentioned in that subsection, but with the substitution for the reference to six equal instalments of a reference to so many equal instalments as there are complete years comprised in that period.

F1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nothing in this section shall apply to any sum to which section 349(1) applies by virtue of section 524(3)(b).