AIB's attempts to discredit claims that it ever had a potential DIRT liability of £100 million have run into difficulty, as the committee has now established that the figure had a ring of truth to it.
The £100 million figure was disclosed to the bank's senior executives in 1991 by its then head of internal audit, Mr Tony Spollen, but was dismissed out of hand.
On Monday Mr Gerry Scanlan, former chief executive of AIB, described the basis for that calculation as "infantile" and "very childish" and said that it could not be accepted. Yet when Mr Jim Culliton, the former AIB chairman, was closely questioned about the basis on which the bank had ordinarily calculated its DIRT liabilities, he admitted that £100 million was not an unrealistic figure to arrive at if you were to apply that formula to the years 1986 to 1991.
But the bank insists that it did not even have to consider doing any such calculation, because the Revenue had agreed to write off any outstanding DIRT up to April 1991.
Each AIB executive who has given evidence so far has told the committee that they believed that the bank had done a deal with the Revenue in relation to bogus non-resident accounts.
Mr Sean Ardagh TD suggested that maybe it was a case that if the bank repeated this often enough it would be taken as fact because, despite its claims, AIB had never obtained written confirmation of the arrangement from the Revenue.
The committee has already heard the Revenue's emphatic denial of the existence of any amnesty. Mr Tony Mac Carthaigh, the senior inspector of taxes who is alleged to have delivered the deal to AIB, has rejected the bank's version of what occurred at the disputed meeting in 1991. He has emphasised that he did not have the power to negotiate an amnesty, as this would have required legislation, and AIB's tax officials would have known this.
Yesterday the bank's in-house taxation experts, Mr Donal de Buitleir and Mr Jimmy O'Mahony, who are both former Revenue officials, took the bank's claims in relation to an amnesty a step further.
They said Mr Mac Carthaigh had explained that the amnesty was being made available to all financial institutions in a bid to get them to clean up their acts in relation to bogus non-resident accounts. They also claimed that Mr Mac Carthaigh had assured them that he had the approval of the board of the Revenue Commissioners to write off its DIRT liabilities up to April 1991.
Mr O'Mahony suggested to the committee that AIB's claim, while not supported by a formal Revenue undertaking, was supported by evidence given to the inquiry by Bank of Ireland and ACCBank about discussions they had had with the Revenue around that time.
Mr de Buitleir and Mr O'Mahony will no doubt give a more detailed explanation of their understanding of what was agreed with the Revenue when they appear before the committee again next week. After that it will be open to AIB and the Revenue to cross-examine each other on the disputed events in a bid to establish whether or not AIB now owes up to £100 million.
Today it is the turn of the former ministers for finance to explain their actions in relation to DIRT. The Fine Gael leader, Mr John Bruton, and the former EU commissioner, Mr Ray MacSharry, will be first to take the stand and will deal with the introduction of DIRT in 1986. They will be followed by the former Taoiseach, Mr Albert Reynolds, the Taoiseach, Mr Ahern, and the Labour Party leader, Mr Ruairi Quinn.