Eighteen people with tax liabilities arising from exercising share options had total outstanding taxes of €88.5 million at the year's end, according to the Comptroller & Auditor General's report.
It said the liabilities owed by the 18 included one very large case.
"A particular difficulty arises in many of these cases due to the individuals concerned having left the country. Seven of the 18 cannot be located and are understood to be abroad."
"In the remaining 11 cases examined where the individual had been located, whether in Ireland or abroad, none of the outstanding liabilities had been collected to date." Five cases were under appeal.
The report shows that at the end of March 2004, there was €1.3 billion in outstanding taxes, of which the Revenue estimated €1 billion would be collected. However, the C&AG, Mr Purcell, questioned the method by which the Revenue arrived at its estimate.
The report examined 310,000 people who had outstanding income tax, including 14 people who had outstanding taxes totalling €92.8 million.
During 2003, €119 million in taxes was written off, down from €178 million the previous year. Of the total written off, €39 million was written off because it was uneconomic to pursue.
The number of cases involved was 38,844 out of a total of 119,607.
The Labour Party spokeswoman on Finance, Ms Joan Burton TD, pointed to the fact that the report showed only six cases of tax evasion going to court in 2003, with no-one going to jail.
"This is in stark contrast to the situation in regard to social welfare fraud, where in 2003 the authorities took more than 200 cases to court, as a result of which 11 people were jailed," she said.
