There's two I get regularly. One is from people pretending to be the Canada Revenue Agency. The other is a message in Cantonese, that according to my coworker who gets them too, is from someone pretending to be from the Chinese embassy basically saying the same thing as the fake CRA one. That you owe money and a lawsuit is being prepared under your name, without actually mentioning your name. The one from the 'CRA' is almost comical. It sounds like something a child would say. I've talked to the government enough to know how they talk. They also don't use odd voice concealing effects typically.
I actually called the number the CRA one left back once and a person with a French accent answered pretending to be from the CRA. I just said if they called my number again I was going to report them to the rcmp and then hung up. It stopped for a few months after that. I'm assuming if it was actually Canada revenue, they would have called back. All I was getting were the Cantonese ones. The CRA ones only started again recently.