The owner of a office supply business in Tralee, and "a generous" charity worker, was found to have almost €800,000 in Swiss and other foreign bank accounts.
They were uncovered on foot of a Revenue investigation and a European tip-off.
John Cashell, 59, of Stacks Mountain, Kilflynn, Co Kerry, had been a director of Radley Cashell Business Systems Ltd at Rock Street, Tralee.
He pleaded guilty in relation to three counts of incorrect income tax returns, in 2001, 2002 and 2003, with regard to undeclared interest on these accounts.
The matter centred on the Isle of Man and subsequently in Switzerland and the banks included the former Close Bank, AIB and Irish Permanent.
In May 2003, €529,000 had been transferred from Close Bank in the Isle of Man to a Swiss bank when Close Bank closed, John Flynn, Assistant Principal, Investigations and Prosecutions Division with Revenue outlined to the court.
Mr Flynn had conducted investigations in the Isle of Man, as well as at Mr Cashell's home, under warrant in 2011.
The court heard Mr Cashell had already been found to have six domestic "bogus non-resident accounts" in AIB in October of 2002 following a previous an investigation by Revenue.
He had not availed of the amnesty offered in 2001 in relation to these kind of accounts and had paid €250,000 in settlement. He had his name published on foot of a Revenue investigation.
Mr Cashell's returns made no reference to the €798,000 in foreign banks in his returns of income.
In 2010, as part of mutual legal assistance from the French and Spanish, Revenue became aware of a Swiss bank account held by Mr Cashell and a search under warrant by Mr Flynn unearthed the Isle of Man accounts.
When questioned about these, Mr Cashell essentially gave "untrue and evasive answers", Mr Flynn told prosecutor Tom Rice.
He has paid over €100,000, which was the amount due in tax, interest and penalties on the three accounts, the court was told, with €72,000 of this being paid today by cheque.
However, a further tax bill in relation to 1997 to 2002 of €246,000 is now with the appeals commissioners, the court was also told.
"Revenue were faced with someone who seemed to be involved in systematic tax evasion," Mr Flynn said in the course of cross-examination by defence barrister Michael Bowman.
Mr Bowman also put it to Mr Flynn that his client only owned 45% of the offshore monies and the rest was owned by his subsequent father-in-law Mr John Hickey, who had been a builder in the UK.
However, Mr Flynn said Revenue rejected this.
Mr Cashell, a father of five, had built up his business from a small scale office supply business in 1985 to one which employed 12 people at its peak.
He was no longer involved and the company had been dissolved in 2013. He had suffered loss of reputation and status.
Testimonials from the business community in Tralee spoke of his charitable works for Goal, for Lesotho, and the Society of St Vincent de Paul.
Paul Hanrahan, who is involved with the African Lesotho charity raising funds for subsistence farmers, said Mr Cashell was "the most generous man" he ever knew.
Retired businessman and Lyons Club member Chris Nugent said Mr Cashell had done excellent work for his community.
Speaking of the effect on Mr Cashell, Mr Nugent said "the Revenue will take its toll on anybody. It will depend on your status in society and how you handle it".
There were also written testimonials from members of Tralee Chamber of Commerce.
Judge Carroll Moran said he would adjourn sentencing to October to allow the latest cheque of €72,000 (part of the €100,000 penalty on the three counts) to clear.
The judge said he would wish to see a current set of accounts as either a fine or a prison sentence of a maximum of five years were options.