The Irish Fiscal Advisory Council (IFAC) has estimated that if the Government was to adopt the main recommendations of the Commission on Taxation, it would raise an additional €15 billion or 5.3% of national income (GNI*) annually over the longer term.
This is based on a technical paper published by IFAC today.
The Commission on Taxation presented its report to the Government in September.
It detailed 116 possible changes to the tax and welfare systems to broaden the sources of taxation.
Some of its recommendations included increasing the Local Property Tax, introducing a site value tax and the restriction of relief from capital gains tax from the sale of a principal private property. It also included changes to VAT and PRSI.
Some of its proposals were criticised at the time by Tánaiste Leo Varadkar.
IFAC said the Government should publish as assessment of how much would be raised by the main policy options set out in the Commission's report.
It said in the future revenue from taxes related to vehicles and fuels are likely to fall as the economy moves to more renewable sources of energy, while spending pressures from the ageing population, such as pensions and healthcare, are likely to rise.
IFAC said its estimate is "optimistic" and does not account for what possible responses there might be to new taxes.
It said a broader debate now needs to take place to assess what the role the State should play in the future and how this should be funded.
IFAC can see big pressures coming on public finances, Chairperson Sebastian Barnes has said.
Speaking on RTÉ's Morning Ireland, he said: "We are going to have to have a discussion about how to raise taxes, overall.
"What we've done is we've taken the proposals from the Commission [for Taxation and Welfare], which touch on a number of different areas and we've tried to put a number on that.
"We reckon that if you put together all of those measures, you get to an increase in taxation around 5.5% of national income.
"That's something for the long term, but it's a very big change in our taxation. It would take us from being a relatively low-tax economy in the European context, more like the UK, to something more like Germany. And within that, there are a number of measures that they have put forward.
"We think they should be considered very seriously by the Government and by the political system."
He said that overall broadening the tax base "is going to be necessary", given higher costs arising from the aging population from pensions, from climate change, and from replacing some of the corporation tax Ireland currently relies on.
Mr Barnes said these measures will have to be considered because broadening the tax base, rather than increasing rates from existing taxes, would probably have a lower impact on growth.
He said there is an important debate to be had about increasing taxes on people’s savings.
"We know that over the past couple of years some people have done very well in terms of savings, in terms of investments, and also people who have houses have done relatively well compared to those who are struggling to get onto the property ladder.
"So, broadening the tax base in this direction is a very useful thing to consider. It’s something that many other countries are considering as well - to broadening taxes, moving it away from taxing income on people’s labour to savings, which may be fairer and more efficient.
"The European Commission is planning to make proposals in that area, and it is an area that should be considered, but a windfall is really, a one-off tax," Mr Barnes said.
