A scam that has targeted elderly Tauranga residents claiming they are in tax arrears and demanding money has prompted a warning from the Inland Revenue Department to be wary of dodgy impostors.

The Government tax department had received more than 500 complaints throughout New Zealand from people concerned by scam calls from people claiming to be from the IRD in the past four days.

On Tuesday, Tauranga octogenarian Claire Acott received a call from someone claiming to be from Inland Revenue and threatening her for money.

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Mrs Acott, 87, was told she would need to call back a certain number straight away and hand over her bank details or she would be in serious trouble.

"It's pretty scary because I'm on my own and I'm a fulltime worrier," Mrs Acott said.

Shaken and a little confused, Mrs Acott called a trusted friend who told her it was a scam.

"I got upset about it because I don't like the idea of someone telling me I owe money when I don't. But there are older people out there who might fall for it."

Friend Evelyn Lloyd, 78, said she had the same phone call a few weeks ago.

"They didn't give a name but they said they were from the IRD and said that I was in arrears for paying my taxes. Then they said if I didn't contact or phone them I would be in serious trouble. I thought, 'Heavens above. I know I don't owe any taxes'," Mrs Lloyd said.

"I'm no doolally. I'm up to the play. I just ignored it. But then Claire phoned me. She was very upset saying, 'I've had a call from IRD saying I owe them money'."

Mrs Lloyd said the person sounded like a mature woman.

"I didn't talk at all. She was straight into it. She told me to phone back or I would be in serious trouble then the phone went down. She didn't give me a chance to say 'who are you?' I dismissed it for me but when Claire rang ... "

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Both women have not complained to Inland Revenue or the police but said they wanted to share their stories because they did not want anyone to fall for the scam.

Inland Revenue's customer services group manager Eleanor Young said the scammers generally allege people are being investigated for historic tax fraud or evasion, before threatening them with legal action.

"In some cases people are told they must pay a debt urgently or face jail, and to avoid that fate are told to ring a Wellington number," Ms Young said. "These callers are quite clever and are particularly aggressive, so people need to be wary of being caught out."

Ms Young said the scammers identified themselves in the way an Inland Revenue representative would "and the request of personal information including the person's IRD number in a very convincing and confident manner".

Inland Revenue would never ask for credit card details or bank account numbers over the phone, she said.

"We recommend that if anyone receives a call of this nature they hang up and if they have any concerns to email phishing@ird.govt.nz."

Too good to be true?

* Common scams are the Nigerian fee scam, prize notifications, internet auction scams, and phishing.

* If something sounds too good to be true, it probably is.

* More information about common scams and how to protect yourself go to the police website, Department of Internal Affairs anti-spam web page, Ministry of Consumer Affairs Scam Watch website, and the Scambuster website.