The number of e-mails from fraudsters trying to take advantage of the tax credits deadline has surged, according to HM Revenue and Customs (HMRC).
The deadline for people to submit their tax credit renewal forms is on 31 July, prompting the latest attempt by fraudsters to gather bank details.
An e-mail is sent suggesting people are due a refund before directing them to a clone of the official HMRC website.
Victims are then instructed to enter their debit or credit card details.
The fraudsters can then empty these accounts of funds, before selling on personal details to other criminals.
More than 46,000 of these e-mails have been reported to HMRC since the first tax credit renewal forms were sent out at the beginning of April.
Some 150 scam websites have been shut down during the same period.
"We currently only ever contact customers who are due a tax refund in writing by post. We do not use telephone calls, e-mails or external companies in these circumstances," said Joan Wood, director of HMRC online and digital.
People are advised not to open any suspicious e-mails, but to forward them on to HMRC before deleting them.