"Call this number or there will be consequences."

The 82-year-old woman from Box Hill in Melbourne, who received the threatening call on Friday demanding she pay a "tax debt" over the phone, is just one of thousands of Australians being targeted by tax scammers.

"Part of the message had been cut off so I didn't catch all of it, but I did catch the part about the consequences," her daughter told Fairfax Media. "It took me by surprise, because I'm used to email scams but this call was quite brazen. It's a disgusting message to leave on an elderly person's phone."

The call advised the woman to immediately phone a NSW number but the woman's daughter, who did not want to be identified, said she suspected the call was a scam. "I thought I'd Google it first to get some background," she said.

Her search revealed 19 other Australian households had been contacted by the same number within the week, all in regard to supposedly-outstanding tax debts or tax evasion.

The Australian Tax Office is reminding Australians to be wary of aggressive tax debt scams during tax time. From January to May this year, the ATO received more than 40,500 phone scam reports. It says more than 220 Australians were persuaded to hand over a total of $1.2 million to scammers.

Assistant Commissioner Graham Whyte said the ATO would never cold call about a tax debt. "We would never threaten you with jail or arrest, and our staff certainly wouldn't behave in an aggressive manner," he said.

Edwin and Annie Fabry, from Gold Coast, were told they had to pay $4300 in tax arrears.

"I told the man that I wouldn't do any such thing over the phone and to put it in writing and mail it to our address, which he already had with our full name and home address," Mr Fabry wrote in an online forum.

The Australian Competition and Consumer Commission urged Australians to hang up on tax scammers following a spike in the number of people reporting that they had lost money to tax scams this year.

More than $1 million was reported lost to the ACCC's Scamwatch website in the six months to June 30. This compares to a total of $1.6 million lost to tax scams last year.

ACCC Deputy Chair Delia Rickard said the scams come in many guises but generally claim that the call recipient has underpaid their taxes and are required to replay the tax debt immediately or face frightening repercussions.

"Tax scammers are particularly aggressive so many people feel pressured to pay quickly without questioning them," Ms Rickard said. "The most threatening scammers even say that police are on their way to arrest you but can be stopped if you pay immediately."

She said scammers often use personal information found online to convince people of their legitimacy. They usually ask for payment for an "unpaid debt" via money transfer, credit card, direct debit cards or even iTunes cards, and calls appear to come from a local phone number but most use Voice over Internet Protocol (VoIP) phone numbers.

The numbers often look like Australian numbers, but are a proxy for a call made through an internet connection.

You can report suspected ATO email scams by forwarding the original email to ReportEmailFraud@ato.gov.au.

You can also report scams to the ACCC via the Scamwatch report a scam page or by calling 1300 795 995.