CRA refers to Stewart as the leading case on “business”

The bigger the question, the shorter the answer. When asked to comment on the meaning of “business” in the Act, CRA provided a response a significant portion of which read:

… Stewart considered how to determine whether or not there is income from a source for the purpose of section 9. In that context, it provided guidance that can also be used to determine whether or not a business exists.

Because Parliament and the courts have given "business" a very broad meaning, the CRA does not intend to give specific guidance.

It may be recalled that in Stewart, Iacobucci and Bastarache JJ. stated:

"Equating the term 'business' with the phrase 'reasonable expectation of profit' does not accord with the traditional common law definition of business, which is that 'anything which occupies the time and attention and labour of a man for the purpose of profit is business'."

Neal Armstrong. Summary of 11 October 2019 APFF Roundtable, Q.17 under s. 248(1) – business.