There is a widespread IRS (or CRA) or "tax scam" being practiced by scammers on both USA and Canadian residents.
USA tax payers should read this:
http://www.irs.gov/uac/Newsroom/Phone-Scams-C ... 5-Filing-Season
Canadian tax payers should read this:
http://www.cra-arc.gc.ca/nwsrm/lrts/2013/l131210-eng.html