I once got a call from someone posing as a CRA (Canada Revenue Agency) agent trying to claim I owed back taxes and if I didn't pay immediately they would press charges. I said something to the effect of "I am glad you called did you get my T5063 amendment in the mail". And the guy goes on again about how I owe these taxes. And I reply "yes, I understand but if you review the T5063 amendment I sent you, you will see you actually owe me $5000 dollars, so when can I expect my payment?" and the guy hung up. That was fun.