5 March 2012 Internal T.I. 2010-0384681I7 - Preamble to subsection 20(1) of the Income Tax Act -- summary under Subsection 20(1)

the applicable-to-source test in the preamble "requires that expenses described in paragraphs 20(1)(a) - (ww) of the Act must be prorated between a taxpayer's sources of incomes and its activities, if any, which do not constitute a source of income."