772.5. An individual who, in computing his taxable income for a taxation year, deducts an amount under any of sections 726.7 to 726.9 and 726.20.2 is deemed, for the purposes of this chapter, to have claimed the deduction in respect of such taxable capital gains or portion thereof as he may specify in the fiscal return he is required to file under section 1000 for the year or, failing such designation, in respect of such taxable capital gains as the Minister may designate in respect of the individual for the year.