851.61. Where, in a particular taxation year, a taxpayer pays all or a portion of a contingent amount referred to in paragraph b of section 851.60 that reduces the amount of the taxpayer’s expenditure referred to in paragraph a of that section, the portion of the contingent amount paid by the taxpayer in the particular year for the purpose of earning income is, for the purposes of this Part, deemed(a) to have been incurred by the taxpayer in the particular year;
(b) to have been incurred for the same purpose and to have the same character as the expenditure so reduced; and
(c) to have become payable by the taxpayer in respect of the particular year.