A former Anglo executive has told the Dublin Circuit Criminal Court that the issue of certain accounts being archived by the bank's IT department first came to light as part of an investigation into loans to directors of the bank, after the bank's Chairman, Seán FitzPatrick resigned.

Walter Tyrrell is the former head of group internal audit at IBRC and is giving evidence at the trial of three former officials of the bank.

Bernard Daly, Tiernan O'Mahony and Aoife Maguire deny trying to hide accounts connected to the bank's former Chairman, Mr FitzPatrick from Revenue.

Mr Tyrrell told the court that Mr FitzPatrick resigned as chairman of Anglo Irish Bank in late 2008 and he agreed that a number of issues arose after that.

He said a number of external agencies and the bank's board wanted to review the issue of directors' loans.

He said he was involved in carrying out a trawl to establish the extent of such loans.

Mr Tyrrell said he became aware of an issue of the archiving of certain accounts.

He said he mentioned it to the new chairman of Anglo Donal O'Connor in late January or early February 2010.

He said the issue of directors' loans was a higher priority at the time and took up more of his attention.

Mr Tyrrell said in March 2010, at a time when the bank had "settled down a little bit" he had a conversation with James Shaw of the bank's IT department and he then approached the bank's chairman again to indicate this was still a live issue.

There were concerns that it should be reported to the Garda Bureau of Fraud Investigation or the Financial Regulator or the Revenue Commissioners.

He said the bank's fraud officer, Patrick Peake carried out an investigation into the issue.

All three former Anglo officials are accused of trying to delete references to two accounts in the name of Mr FitzPatrick's brother-in-law from Anglo's core banking system.

Mr Daly and Mr O'Mahony deny omitting the name of Mr FitzPatrick's brother-in-law from a list provided to the Revenue Commissioners of people who held non-resident accounts in 1995.

Mr O'Mahony and Ms Maguire deny attempting to delete six other accounts, all connected to Mr FitzPatrick, from the bank's core banking system.

Earlier, a principal officer from the Revenue Commissioners told the court that Deposit Interest Retention Tax - a tax on interest earned on a deposit account - was first introduced in the mid 1980s.

It was initially around 20%, the court heard, but was increased to 41%.

Denis O'Connell agreed that the higher the amount of money on deposit, the more tax the depositor would have to pay.

DIRT is deducted at source by the bank.

But he said if someone opened an account in an Irish bank and declared they were not a resident here, they would not have to pay the tax.

Mr O'Connell also outlined the penalties that can be imposed if someone is found to have deliberately not paid tax.

These range from financial penalties to periods of imprisonment up to five years.

He agreed that auditing a business could be complicated, depending on the size of the business involved.

He agreed with lawyers for Mr Daly that an audit of a financial institution would be a very substantial task both for the revenue commissioners and the financial institution and he said it would not be unreasonable for such an audit to take nine months.