In Canada all you need to do is live together in a "conjugal relationship" for 12 continuous months.

Or have a child together. But common-law relationships and marriages are not the same thing in Canada, whereas other places where common-law marriages are recognized, they are legally identical to other marriages.

That's a bit misleading. The specifics vary by province. eg. Common Law kicks in after 3 years living together (in a marriage-like relationship) in Ontario, and after 2 years in BC.

Revenue Canada has their own definition of common law, for tax purposes only (not litigation), which is independant of that and is 12 months.

"I know I’ve seen fiction where it requires little more than cohabitation, but that’s not a real thing."

New Hampshire: Common Law Marriage: "persons cohabiting and acknowledging each other as husband and wife, and generally reputed to be such, for the period of 3 years, and until the decease of one of them, shall thereafter be deemed to have been legally married." (N.H. Stat. §457:39)

So not really a fiction. There aren't many requirements there.

The old law in PA did not even require habitation or a contract. All that would be required aside from regular eligibility stuff would be presenting themselves in public as husband and wife plus exchanging words of intent at one time to be married (verbal contract). That law was active until as recently as 2005.

Your own NH quote, emphasis added: “people cohabitating and acknowledging each other as husband and wife…” It’s not something that happens by accident just by cohabitation, even under that rule.

Your recent PA law is in accord with my point that the rules usually require mutual intent to marry plus public presentation.

"I know I’ve seen fiction where it requires little more than cohabitation"

Emphasis mine. Merely stating you're husband and wife is "little more" in my book. It's pretty easy for people to think you're married, especially if you tell people you're husband and wife to make the conversation easier.

Yes, if you read that one sentence out of context of the immediately preceding one, and the post that the post it is in is responding to, I can understand your response.

Can’t really understand doubling down on claiming it is relevant after having the relevant issue pointed out again, but, you know, you do you.

Whatever. If you actually cared to think and reread, you would see there is more content and context than what you are selectively seeing. That one could in fact be common law married by accident given the NH law if they merely lived together and said they were husband and wife to make conversations easier, as others have admitted to saying in the comments. That's were you have a contradiction/inaccuracy in your comment. NH does not require any proof of shared intent, and with one party deceased they can pretty much rely on how things appeared to the general public, including if you just told people you were husband an wife to make things easier. But yeah, by your own words - you do you.

That essentially just says "if you got married and told everyone you were but never filed the paperwork, it counts." It doesn't seem like, if it came to it, you told a court or government that you weren't married that they'd go "but you are."

It depends on what the charge is. In most cases the government wouldn't care, or they would favor them not being married for tax issues or to void legal protections. They certainly could try to prove you are married, but they would need some reason to want to. It's more likely one spouse would want to prove they it during a divorce.

In NZ cohabitation for 3 or more years usually puts you into a de facto relationship which has basically the same legal status as a civil union or marriage.