Mike Down, of accountancy firm Baker Tilly, said the HM Revenue & Customs (HMRC) should be checking tax returns to see whether individuals had already explained their circumstances.
He told the Daily Telegraph that The Revenue is "adopting a computer says yes approach, rather than simply checking the tax returns".
One case involved an elderly widow whose effective tax rate was low because she was giving more than half her income to charity.
More top news
There's no love lost between Boris Johnson and Theresa May.
Eagle, who was one of 20 members of the shadow cabinet to resign, will formally announce her intention to stand on Thursday.
ITV News visits the rural county in the wake of the EU referendum result and finds increasing frustration with Britain's political leaders.