The government's online fraud agency is warning people to check business invoices over the phone before paying large sums of money.
Scammers have been defrauding people of hundreds of thousands of dollars by gaining access to the email accounts of legitimate businesses.
Known as invoice fraud, scammers monitor a business's emails, waiting for it to invoice a customer for a large amount of money.
They then email the customer, from the business's email address, giving a new bank account number to pay the money into their own.
Rob Pope from the government's online fraud agency, Cert NZ, told Conan Young that it's incredibly lucrative for the scammers.