This number has left me voice mail 3 times in the last two days indicating we owe money to CRA.  The speaker does not ask for anyone in particular, just leaves the voice mail. When you call the number, the person who answers, who is foreign, says thank you for calling CRA.  Since when does CRA give you a direct line, no option for english or french etc...  The voice mail we receive is exactly what sample 3 in the CRA link below regarding sample scams.
http://800notes.com/Phone.aspx/1-613-209-0976

Forgot to mention, the voice mail is a recording, not a live person. The recording is the exact same in all voice mails.

I'm on a roll!  Wrong link was included in my first post.  My apologies.
http://www.cra-arc.gc.ca/scrty/frdprvntn/frdlnttlphn-eng.html

Please be careful!!!! 613-209-0976 A man called me today stated he was from CRA stating that I had a debt outstanding to the government. He was totally unprofessional, asking me my age and wanting information from me. He said documents were mailed to me twice. Told him he could mail them again. When I asked him what address they had, he knew it. Anyhow, told him to mail it again, because I didn't believe her was from CRA. He got mad and stated to tell me "It wasn't his fault that I didn't get it, but I owed money." Weird thing is, "he never told me how much I owed."

Same as above.  East Indian accents and very rude.  I don't owe anybody anything, so it's definitely a scam.