Reported that he is calling from Tax Crime and Investigation Unit. He identifiied himself as Officer David Miller, who had a South Asian accent, reported that there was a fraud case and demanded money to be sent to them. Instructed that I needed to get a voucher and to send it to them by fax. If i didn't i would be arrested.

Normally, the CRA has explicit instructions how to pay any money to them accordingly..by faxed voucher is not. So please be careful and be aware of the redflags.

Guy with a south asian accent said he's from the canada (revenue?) agency, about an allegation of tax fraud and call back the hotline at 613-699-3487. It's BS

Same BS as above, threatened seizure of our house.  Call display shows a CRA 800 number for self-serve questions.

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

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

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

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

UPDATES:
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

Caller identified himself as Kevin Roy (Asian with bad accent) with CRA (Canada Revenue) requesting we call him back at 613-699-3487 imediately to avoid a CRA legal petition that is being issued regarding tax fraud by us.
I identified this as a SCAM as I have dealings with CRA on a regular basis and called CRA to verify as they only communication via letter.  Yes it is a SCAM.