I do not know if, these days, interviewers are routinely asking applicants if they filed income tax returns in Canada, but a few observations are warranted:
-- more than a few anecdotal reports indicate that employment and tax filing questions have come up during the interview even if this is not usual
-- changes in law governing information sharing apply to all applicants, even applications made prior to June 2015; this facilitates the exchange of information between departments of government
-- my sense is that there are various scenarios which are more or less likely to trigger questions as to employment and tax filings
-- nonetheless, the requirement to have complied with tax filing obligations in four out of the six tax years preceding the date of application only applies to applications made after June 10, 2015
My sense is that IRCC can and more than occasionally does ask questions related to employment and tax returns. I had actually submitted copies of my NoA for all the relevant years with my citizenship application. There was no mention of this at my interview, though I was asked some questions about my employment. That was nearly two years ago.
Post-June applicants obviously must have filed returns (with some exceptions).
Pre-June 2015 applicants who did not file Canadian tax returns should go to the interview prepared to answer questions about their income, their employment, and to reasonably (but also truthfully of course) explain why no tax returns were filed. It might not come up. It very well might come up.
While generally it appears it rarely (if ever) helps to bring extra documents to the interview (that is, documents in addition to those the applicant is instructed to bring), it nonetheless seems prudent to bring Notices of Assessment for the relevant years, assuming of course tax returns were duly filed and the NoA was received. They do not add up to much paper, and perhaps just referring to the fact of having them could make a difference. (I doubt it is a good idea to have a big stack of additional paper, but a few key documents is easy to carry and manage, just in case there is an opportunity to resolve a question sooner rather than later.)
Obviously, though, if IRCC has questions about whether an applicant has been employed in Canada, or has some undisclosed employment abroad which is the source of income supporting the applicant, they can and will engage in inquiries as to tax return filings and potentially ask for NoA in addition to other employment related documentation. That is, whether or not most applicants are asked about filing tax returns, some are, and the scope of the subsequent inquiry can lead to some rather intrusive requests for documents. And now IRCC has legal authority to verify much of the information submitted directly with the CRA.
