Joined: Mar 2009
Posts: 5038
Phone numbers are easy to spoof.
Canada Revenue (or any other government department for that matter) generally won't contact you by telephone unless it's following up some form of written communication (i.e. a letter, you sent in a form or application, etc). If you're unsure, you can ask them to send it in writing. If it's legit, that won't be an issue.