These include the power to listen in on people’s private phone calls.
They can also intercept emails and place listening devices in people’s cars.
The new powers have come into effect following the passage of the Serious Crimes Act.
The Revenue & Customs now has similar surveillance powers to MI5 and the police.
Many of the new powers were previously available to Customs officials but have now been extended to their Revenue colleagues.
The Act was given the Royal Assent in October and came into effect last month.
The Revenue says that the new powers do not apply in ordinary cases and will be used only in serious crimes.
Nevertheless many tax inspectors have been trained in surveillance techniques.