I am not qualified to give personal advice. Not for citizenship or immigration questions. And for sure not at all for tax questions. I do not know and am not qualified to figure out what years any particular individual needs to file a Canada tax return. That said, in GENERAL terms, any tax year in which a person has Canadian source income is very likely to be a tax year that CRA rules require filing a tax return. And if CRA asks for a return, for CRA that is a year the individual is obligated to file a return.
But that in turn has NOTHING to do with grant citizenship requirements.
The grant citizenship requirements do not depend on filing a tax return. They depend on complying with CRA tax filing rules for at least three of five years.
Even if it should be easy to apply the rules to your situation, that's not what I do. Because I am not qualified to do that. For lots of reasons. I can reiterate what the rules are. For someone who applies this month, May 2020, the relevant five years are: 2015, 2016, 2017, 2018, 2019, those being the FIVE relevant tax years preceding the date of application.
To meet the tax filing compliance citizenship requirement, the applicant needs to show compliance in any three of those tax years. Obviously, for any year in which the applicant did file taxes, the applicant can check [yes] and [yes], as in yes, required to file, and yes, did file. All the years for which the applicant checks [yes] and [yes] count toward the three year compliance requirement.
But any year for which the applicant checks [no] and [no], no, not required to file, and no did not file, also counts as a year in compliance.
Right now, this year, CRA has changed the rules for 2019. As I recall, no one is yet required to file a return for 2019 (deadline to file is June something as I recall). So anyone applying this month can honestly answer, for the tax year 2019, [no] and [no], no, not required to file, and no did not file, and it will count as one of the years in compliance . . . even though it will later be the case they will be required to have filed a return for 2019. I hesitate to remind anyone of this wrinkle, since just the distinctions about complying with the tax filing obligation versus actually filing a return tends to cause confusion enough. And this wrinkle is both temporary (if the applicant waits to apply in July this year, May most years, odds are the correct response for the previous year is [yes] required to file) AND NOT a particularly good idea after about mid-February (when most taxpayers should have all the necessary and relevant information needed to file a return and CRA is open to accept the previous year's returns). But for purposes of the more recent queries here it illustrates that what matters for the grant citizenship requirements is compliance with CRA rules. Again, the question is not how many years the applicant filed a return. The question is about how many years the applicant complied with CRA tax filing obligations.
Leading, somewhat to the first part of your query:
Again, I am NOT qualified to evaluate let alone advise anyone about their personal tax filings with Canada. I rarely see any hint of anyone posting here who is.
Moreover, as I have often emphasized, who, when, and what, relative to tax filing requirements, is very individual, pursuant to which many individually specific factors are considered in conjunction with a range of criteria employed by CRA to make such determinations.
But some of the CRA rules are fairly simple:
For example, a person living and employed in Canada during a tax year will almost certainly be obligated to file a tax return for that year.
Anyone with Canadian source income for a given tax year is usually obligated to file a return for that year.
For another example, one directly from the CRA website: anyone CRA asks to file a return for a given tax year is obligated to file a return for that year.
CRA can be mistaken. Happens. Happens more often than it should. Bureaucracies tend to be like that. (Have I ever mentioned that "bureaucracy is what bureaucracy does?" Oh, wait, that's in my signature here.) But, at the very least, if CRA asks for a return for a given year, it is presumed that yes, indeed, the individual is obligated to file a return for that year. It tends to be easier and costs less to file a return than to challenge a CRA claim that a return is required. REMEMBER: what sort of return, what forms and schedules to include, what income to report, what credits or deductions to claim, what tax must be paid, all that varies even more widely.
So, basically, for any year that CRA requests a return, the safe answer for such a year is [yes], as in yes, required to file a return for that year. Whether or not to also check [yes] in the second column, as in yes, filed a return, depends on whether or not a return was actually filed.
I realize this tends to make things sound a lot more complicated than necessary. This is intentional. Even though the simple answers are usually right, they are NOT always right. The tricky part is knowing when there is a difference and avoiding pitfalls lurking in the nuances. For tax questions, lots of nuances, lots of pitfalls, lots of individual quirks. It is important for each individual to do his or her own homework and sort these matters out for himself or herself. Taking shortcuts tends to risk things going awry.
But, OK, the PROBABLE situation is this: if you properly filed returns for 2015, 2016, 2017, and 2018, you can check [yes] and [yes] for all those years and that is four years in compliance, not just three. And even if you have not filed for 2019 yet, you can check [no] and [no] and 2019 will also count as a year in compliance (as long as you apply before this year's deadline to file a return).
Personally I'd proceed to file 2019 before applying. There is no rush to apply right now. IRCC has a stack of unopened applications already, and it is going to take time for them to get to the new applications . . . but when they do, they will probably work their way through and catch up, still slow and way behind the usual processing timelines, but catching up enough that waiting longer to apply right now will probably not add much if any time to when they get the application processed.
As to why CRA said you were required to file all those years, I do not know. If you have properly filed returns for those years, it's done, history.
