63.For the purposes of sections 271, 274, 276 and 277 of the Taxation Act (chapter I-3), where a taxpayer owned, on 31 December 1971, a property that could have been his principal residence within the meaning of the said sections but for the fact that before 1972 he commenced to use it for the purpose of gaining income therefrom or from a business, he may elect in his fiscal return for the 1974 or 1975 taxation year to be deemed to have so commenced to use such property on 1 January 1972.