It is "probable" that two or more companies may each be contributing at least 10% or more to Ireland's corporation tax revenue each year, a new report has claimed.
The analysis by the Parliamentary Budgetary Office at the Houses of the Oireachtas warns that this means that changes in the business operations or tax strategies of such firms would have a significant impact on Ireland's fiscal health.
The report says there is limited amounts of information available about Ireland's largest corporate tax payers.
But it says that based on what is, the concentration of Ireland's corporation tax receipts amongst the top ten taxpaying corporate groups appears to be significantly above average internationally.
"Therefore, Ireland's CT revenue appears to be exposed to a substantial level of concentration risk," it explains.
The study says there is a level of churn in the top ten taxpayers although this may be less regular amongst the top five or six taxpayers.
"It is unclear if the replacement and replenishment of major taxpayers or the 'pipeline' of incoming FDI companies partially offsets or significantly mitigates the level of concentration risk," it finds.
The study finds that the performance of individual large firms can significantly impact corporation tax receipts and this is a high risk to Ireland.
It also warns that the movement of businesses to other countries can affect revenues coming from corporation taxes, although this is seen as a low risk.
"Given the fact that Ireland has a track record in attracting foreign MNCs, many of whom perform high value-adding functions in the state, a large-scale exit in the short term is unlikely," it says.
The authors highlight that that absence of adequate infrastructure and housing here in Ireland could lower the country's attractiveness for foreign direct investment (FDI) and again this is considered a high risk.
"To mitigate the risk of reduced CT receipts, it is important that Ireland continues to make strategic policy decisions that will enhance its competitiveness in non-tax areas such as infrastructure," the research states.
Also high risk is the ongoing changes to the global tax regime which could also affect the attractiveness of Ireland to multinationals corporations, leading to a reduction in taxes from such firms, it warns.
"There is still a large degree of uncertainty regarding the direction and size of the potential impact of these changes on Irish CT receipts," it explains.
The possibility that intellectual property assets could be relocated from Ireland to other countries is also a risk pointed to by the report.
This it warns could lead to it becoming less important for multinational firms to be located in Ireland which in turn could result in reduced corporation tax revenue.
"These sorts of transactions could reduce the amount of intangible assets in Ireland and therefore reduce the amount of profit allocated by MNCs to the state," the authors write.
"However, thus far this phenomenon has not developed into a major trend."
Income from corporation taxes has grown 23% on average each year between 2014 and 2022, before it stabilised last year, the analysis says.
It finds that while there has already been significant reform of the global tax system through the OECD brokered BEPS project, tax income from businesses has continued to climb.
Ireland has benefited from the expanded overseas activities of multinationals which have based themselves here, it says.
And as part of this process, large US tech firms have transferred much of their intellectual property to this country, boosting tax revenues.
In particular it highlights exports of computer services, which leapt from €32bn in 2012 to €196bn in 2022.
While in the pharma sector, corporation tax receipts have grown from €2.645bn in 2021 to €5.536bn in 2022.
