I got a call saying it's Canada revenue and it's time sensitive etc, is this a scam?

Sounds very suspicious to me.  If you have a tax problem, I think you could expect a letter, not a phone call.  The "time sensitive" phrase is not what CRA would say in a message. Sounds like a threat, or meant to be scary.  CRA probably does not care if you take your time.  If you take more time, they just tack on more interest.