A special campaign by the Revenue Commissioners targeting the construction industry has yielded more than €50 million in additional taxes and penalties in its first five months of operation.
The project, which involves a quarter of Revenue's auditing and compliance staff, has already resulted in the audits of 1,362 construction firms to date.
These audits have yielded €48 million in taxes, interest and penalties.
The Revenue Commissioners have also taken in an additional €4 million from assurance checks.
According to the latest figures available, the campaign has included 46 audits on large property developers and major infrastructural projects with values of greater than €10 million.
Officials have also carried out 361 site visits, covering contracts worth in excess of €1 billion.
The campaign has arisen out of concern about the level of tax evasion in the construction industry, which now accounts for €30 billion or a quarter of GNP.
The sector employs nearly 300,000 people and contributes €10 billion per year in taxes and levies to the Exchequer.
The main focus of the audits is on VAT and the payment of sub- contractors, including foreign construction firms.
To avoid income tax evasion, main contractors are required to withhold 35 per cent relevant contract tax from subcontractors who do not have the required documentation.
In addition, Revenue's special unit dealing with high net worth individuals is to target between 15 and 20 of the wealthiest people in construction and property in the country.
They are part of a group of 300 people with a net worth of at least €50 million, which are monitored by the high net worth unit established by the Revenue Commissioners in 2004.
New figures show that since the unit became fully operational in 2005, it has carried out 40 investigations and audits, which have yielded €23.1 million in additional taxes and penalties.
The figures were provided to Labour finance spokeswoman Joan Burton in a parliamentary reply by Minister for Finance Brian Cowen.
They follow the largest published tax settlement last week, which involved construction firm Bovale Developments, which is owned by brothers Mick and Tom Bailey.
The record settlement of €22.17 million from Bovale Developments includes tax owed of almost €12.5 million and interest and penalties of almost €9.7 million in a case that arose as a result of the Flood tribunal.
In 2002, the tribunal found that the Bailey brothers had obstructed its work by giving a false account of meetings with a key tribunal witness.