The Public Accounts Committee has heard that €61 million has been yielded by Revenue following a tax review of medical consultants which it began in 2010.
Revenue Chairman Niall Cody said the review began following an examination of one medical consultant's tax compliance.
The individual in question was running a private practice from public hospitals.
Responding to Fianna Fáil's Marc MacSharry, Mr Cody said the examination of consultants incorporating and setting has yielded money in 276 cases.
Some of the claims included expenses for nannies, private home expenses and in one case, wages for a child who worked on a website because the consultant was not proficient in IT.
"These are people with significant incomes and there's been significant underpayment of their tax", he said.
Responding to Sinn Féin TD David Cullinane who asked if there are likely to be similar problems in other areas such as landlord pooling their profits into companies to avoid paying the full rate of tax, Mr Cody said he was "tempted to say absolutely".
However, he qualified his reply by comparing Revenue to an anti doping sports organisation.
"If it's serious we can go back a long time", he said.
