AIB has put the Public Accounts Committee on notice that it intends to vigorously defend the amnesty for unpaid DIRT it believes was agreed with the Revenue in 1991 and it will not allow its executives to be badgered.
Since details of a potential £100 million DIRT liability at the State's biggest bank were leaked to the media last year, AIB has been preparing its defence.
Yesterday its group chief executive, Mr Tom Mulcahy, told the committee the bank certainly had some problems in relation to bogus non-resident accounts but insisted any potential liabilities were substantially less than £100 million.
Mr Mulcahy outlined the steps taken at the bank to clamp down on the use of non-resident accounts by customers seeking to evade tax in 1991.
Much of the day's proceedings were taken up by the committee's "star" witness, Mr Tony Spollen. It was his leaked memo which contained a DIRT estimate of £100 million which triggered the inquiry.
Mr Spollen had worked at AIB for over 20 years, spending the last five years overseeing the bank's internal audit functions.
He left the bank in 1991 a few months after he began to exert increasing pressure on AIB's senior management to address the widescale abuse of non-resident accounts throughout its branches.
The committee spent a long time trying to establish how Mr Spollen arrived at the £100 million figure and to examine the circumstances leading up to his eventual departure from the bank.
The Comptroller and Auditor General's report details frequent correspondence between Mr Spollen and AIB's then finance director and head of retail banking where he points to the bank's massive problem in relation to compliance with DIRT.
After lengthy questioning the committee was told that Mr Spollen first learned about the scale of the bank's bogus non-resident accounts in January 1991.
And he asserted that it would be "scurrilous" to imply that his actions thereafter were motivated by anything other than his desire to do his job.
The committee also referred to another internal AIB document which totally rebuts Mr Spollen's £100 million estimate.
Even today, AIB claims any DIRT liabilities due at that time could amount to between £25 million and £35 million.
Mr Spollen was then questioned on the controversial tax "deal" which the bank's taxation team believes it brokered with the Revenue.
AIB's understanding is supported by contemporaneous notes made by its internal taxation specialists after a meeting with the Revenue Commissioners.
The bank believes the Revenue agreed to be "forward-looking" and was prepared to write off any unpaid DIRT on bogus non-resident accounts up to 1991 based on an undertaking by the bank that the practice would stop.
On learning of this discussion, Mr Spollen said he was keen to get the details of the Revenue's position on paper but the bank's tax officials advised against it.
The Revenue is maintaining that no such deal was ever done.
The bank's team which claims to have negotiated this deal includes a former inspector of taxes, Dr Donal de Buitleir, who will face the committee on Monday.
Judging by yesterday's proceedings Dr de Buitleir and the other bank executives who have to face the committee on Monday can rely on the swift intervention of the AIB's legal counsel, Mr Dermot Gleeson, if they are faced with questions which he deems inappropriate.
When the hearings move into cross-examination, Mr Gleeson will also have the opportunity to carefully question the Revenue officials who are disputing AIB's version of events.
AIB seems to have used its time well in preparing for the hearings.