Denis O'Brien has taken up an address in Malta, the Mediterranean island which charges no tax on assets or income not brought into the jurisdiction.
The move comes as Mr O'Brien is preparing for the flotation of his Caribbean telecoms company, Digicel, on the New York Stock Exchange, a deal that could net him up to €1.5 billion.
A spokesman for Mr O'Brien said he had no comment to make on the use of the new address. Mr O'Brien has homes in Portugal, Dublin and Thomastown, Co Kilkenny.
Mr O'Brien moved his tax residency to Portugal in the period prior to the sale of his Irish business, Esat Telecom, to BT in 2000, which netted him more than €300 million but on which he did not pay capital gains tax.
At the time a provision in the tax treaty between Portugal and Ireland meant he could not be levied with Irish capital gains tax.
In a filing to the Companies Registration Office in March, giving notice that he had taken up a directorship of a technology company, the Norkom Group, Mr O'Brien's "residential address" was given as Flat 6/60, Suite F, Tigne Street, Sliema, Malta.
According to international tax consultants Henley & Partners, Malta "is one of the most attractive locations in Europe for tax-advantaged private residence.
"There is no tax on worldwide income or assets, so the permanent resident's global income, when kept outside Malta, is not taxed in any way."
To qualify, persons have to buy or rent a property with a certain minimum value, and visit Malta at least once in the first 12 months of holding the status.
"A permanent resident enjoys a privileged tax status while at the same time benefiting from Malta's wide network of double taxation treaties. As long as the resident abides by the rules of the permit, the permanent resident need not spend any particular time actually residing in Malta," according to Henley.
Earlier this week, Mr O'Brien resigned, with immediate effect, from the position of deputy governor of the Bank of Ireland, citing the demands of his international business interests.
His role at the bank takes up to three days a month, according to sources, who said Mr O'Brien is concentrating on the flotation of Digicel later this year, and building a separate mobile business in the Pacific.
Sources close to Mr O'Brien pointed out that he had been in Trinidad three times in the past few weeks.
Mr O'Brien has also resigned from the Norkom Group and the Smurfit Business School. His spokesman said the resignations were unconnected with the work of the Moriarty tribunal, which is looking at the awarding of a mobile phone licence to Esat. The tribunal is expected to publish a report next year.
Mr O'Brien owns in excess of 87 per cent of the Digicel group, which is owned by way of Digicel Ltd based in Bermuda, another territory with an attractive capital gains tax regime.
