Inland Revenue is warning of an aggressive phone scam threatening people with deportation or prison if they don't pay up.
The manager of customer services, Pat Crawford, says it has received 18 reports of customers being called and accused of owing money. One man has been duped of $6500.
Mr Crawford said the scammer asks for a deposit to be made into what is a fake bank account at New Zealand Post or for money to be loaded onto a Prezzie card.
Some victims are being called repeatedly by the scammer and abused in a foreign language, he said.
The scammer's caller ID is identical to Inland Revenue's 0800 number.