Yes, it is a scam
In fact, it is probably the "best advertised" scam on all media!
The best defense is education ... educate everybody you know ... use the following info to educate yourself.

The IRS does not initiate communications
with a "cold call" to unsuspecting people.
Instead
The IRS always sends snailmail letters first!

There is a widespread IRS (or CRA) or "tax scam" being  practiced by scammers on both USA and Canadian residents.

USA tax payers, click on the "USA_Info" link, below, for lots of information and a reporting site.

USA_InfoUSA tax payers should read this:
http://www.irs.gov/uac/Newsroom/Phone-Scams-C ... 5-Filing-Season

Short answer:
The IRS never initiates a contact via phone.
They always send a snailmail first.

If you were contacted by an IRS impostor, you may file a report, after clicking on this link:
http://www.treasury.gov/tigta/contact_report_scam.shtml

Recent news story:
http://www.wltx.com/story/money/2015/03/12/fa ... -scam/70202814/

Congressional hearing:
http://www.nbcnews.com/business/taxes/tax-imp ... hearing-n341906
Canadian tax payers should read this:
http://www.cra-arc.gc.ca/nwsrm/lrts/2013/l131210-eng.html

This scam is also described as scam #11, here:
http://phonehelp.2truth.com/facts.html

~~~~~~~~
Please reply to this post, to let us know you read it, or have taken suitable actions to protect yourself.