The caller ID that appears when the scammer calls is identical to Inland Revenue's customer services number, said Mr Crawford.
"Just to be clear, Inland Revenue will never call customers from our 0800 number or demand payments to be made through NZ Post, a Prezzie card or within 30 minutes," he said.
Mr Crawford said recently a customer contacted Inland Revenue after they were instructed to make a payment.
"Out of fear they went to a NZ Post shop to pay the money demanded. They only realised they were being scammed when asked to load their money onto a Prezzie card."
He said since this time, the victim has continued to be called by the scammer and been abused in a foreign language.
"This is an example of how aggressive and threatening these scammers are. They are deliberately using Inland Revenue's brand to trick customers into paying money they do not owe."
Mr Crawford urged customers who were suspicious to hang up.
"If you have replied to and given money or provided personal details please contact your bank or credit card provider immediately."
Inland Revenue was continuing to work with phone companies and the New Zealand Police's National Cyber Security Centre to track the hoax number so they could shut it down as soon as possible.