There doesn't seem to be uncertainty on when common law started since OP said July 22, and signed off on it. Now they have to prove that they were not common law until later, and prove it. As we both mentioned they need a lawyer. They may get lucky.
I'm not disagreeing. I'm making a slightly different point, that some leniency on the part of IRCC is not impossible, if the claim is made - variously [ we didn't realise / it's complicated / we did not make to wish false claim of marital status / etc.]
Note, uncertainty as much on my part on what to say - we don't know. It's rare. But it's possible.
See the other side of the coin is that they clearly weren't intending to misrepresent here (they told the truth about the July 22 date) [so arguably couldn't have intended to misrepresent before, when they would have known even less than now.]
Again: not a magic bullet. Chances are low. But the whole 'intention' aspect of misrepresentation is murky.
And as side note why I think the 'lifetime ban' for this especially for common law (given that common law isn't even consistent between the provinces and the feds!) is overly harsh. And possibly can be challenged in many respects, because IRCC generally just assumes misrepresentation is automatic, when it requires both materiality and (I think) intent. If I were a lawyer and inclined to pursue this, seems a colourable challenge claim could be made on basis eg "we looked it up and in Ontario where we live it's three years, so we had zero reason to believe it even could be just
one year for immigration purposes." Etc.
I mean, there's some argument to be made that even a relatively sophisticated person could look things up,
properly read that provinces have jurisdction over unmarried cohabitation relationships (and family law generally), and miss the fact that the feds have their own definitions for their own purposes but specific only to some domains (tax, immigration).
Bluntly, it's bloody confusing even for Canadians that grow up here. If intent is required for a harsh punishment under misrepresentation (which I mean as a question, even though one most people would think 'should be' on the basis of just fairness), then there's a plausible case there. (Plausible does not necessarily mean a good one, mind)
Anyway: overall I think this still means low chance of success, but worth trying - as on the 'next level' part of the argument, IRCC implementing a pure 'blanket rule' for all such cases may make it even more vulnerable to a challenge (i.e. if discovery and processing notes could show that this blanket rule helps demonstrate that there is no reasoning nor consideration of either materiality or intention). So I suspect they do not have and realize they could not maintain such a blanket rule.
Wow should stop. Too much coffee apparently.
And repeat caveat: I'm not a lawyer, although acquainted with legal aspects/have had to deal with lawyers a lot - so I could well have misinterpreted something basic or missed something. Not legal advice, my opinion, etc.