The potential impact of Irish reunification on the public finances remains “highly uncertain” with estimates for annual costs varying from €3 billion to €20 billion, the Minister for Finance has said.
Opening a Dáil debate on the fiscal implications of a united Ireland on Thursday, Simon Harris said studies varied so much because they relied on different assumptions.
A study from Dublin City University and Ulster University last year estimated reunification would cost an initial €3 billion a year to the State. It suggested a “unified economy” could reach a fiscal break-even within five to nine years.
However, research by the Institute of International and European Affairs in 2024 presented a “much more pessimistic” outlook, estimating a cost of up to €20 billion annually for up to two decades.
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A Department of Finance 2024 report found the fiscal deficit in Northern Ireland was in the region of £7 billion in 2020.
Harris said it was neither possible nor intelligent to “produce one singular figure” as it was a “much more dynamic situation”. The fiscal deficit in year one would be significant, “regardless of how we wish to cost it”.
Pointing to the current fiscal situation, he said “in 2025, total net tax receipts in our jurisdiction amount to €106.5 billion” but this masked the underlying Government deficit last year of €7.1 billion.
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“An annual cost of €3 billion would amount to less than 3 per cent of total tax revenue, while an annual cost of €20 billion would be equivalent to almost one fifth of all tax revenue receipts.”
The range of estimates matter, because either figure “would clearly have a material impact on the public finances affecting not only the headline budget position but also the underlying fiscal balance”.
However, Harris said while the costs of transition to a united island were important considerations, the question was “not simply what a united Ireland would cost, but what a united Ireland could create”.
Sinn Féin enterprise spokeswoman Rose Conway-Walsh told the Tánaiste “I think Michael Collins would be pleased with you”.
Party leader Mary Lou McDonald commended his presentation of the issue, describing it as “refreshing” and “exactly where we need to be”.
The Tánaiste said a move to the euro would be “an important structural advantage”, eliminating exchange rate risks, reducing transaction costs and simplifying cross-Border trade and investment.
There were “significant opportunities” in services, which accounted for most economic activity “across these islands”. Constitutional change “would provide businesses across the island with seamless access to one of the world’s largest integrated market services”, the EU single market.
Labour mobility “would also become a powerful driver of economic growth” and a united Ireland would result in more coherent investment in education and apprenticeships.
But the greatest economic dividend would perhaps be most visible in the northeast and northwest, he said.
“For too long counties such as Donegal, Derry and Tyrone have found themselves at the edge of two separate jurisdictions rather than at the centre of one coherent economic region.”
But he warned any assessment of reunification must be “firmly rooted in the context of our fiscal position and indeed the level of taxation borne by citizens and businesses”.
The Sinn Féin leader said “Irish unity represents the greatest economic opportunity in the history of the island”.
“It cannot be missed. It must be grasped. The question is not whether we can afford Irish unity. It is whether we can afford partition any longer.”
There was an opportunity to build “one robust economy” working for everyone.
But McDonald said the Tánaiste’s initiative in having the debate makes the position of Fianna Fáil “all the more striking, all the more extraordinary and frankly all the more inexplicable”.
Social Democrats deputy leader Cian O’Callaghan said there were “real challenges in any transition to unity, but there are also very significant opportunities”.
“The future of this island should not be reduced to a balance sheet,” he added.
Labour finance spokesman Ged Nash said he “detected a timidity at Government level” about how to advance the objectives of the Belfast Agreement, signed in 1998.
“Accommodations will have to be reached with those who disagree with us and we need to be honest and upfront about that.”
