I am advised by the Revenue Commissioners that the Revenue Statistics webpage (http://www.revenue.ie/en/about/statistics/index.html) contains a detailed section in relation to the Exchequer cost of many of the allowances, reliefs, exemptions and tax credits available under the Tax Expenditures section of the page: http://www.revenue.ie/en/about/statistics/index.html#section9.
These tables cover statistics up to 2014 in some cases and updates will be published in due course.
The Deputy may wish to note also that, in accordance with requirements under the EU Budgetary Frameworks Directive, my Department will shortly produce a Report on Tax Expenditures which will set out a list of those expenditures and the revenue foregone in respect of them in the most recent year for which figures are available.