The Commercial Court has heard IBRC is suing former auditors Ernst and Young over its handling of alleged transactions by ex-chairman Sean Fitzpatrick.
The bank has succeeded in having the multimillion euro case fast tracked to the commercial division of the High Court.
Ernst & Young received fees of over €9m for auditing the former Anglo Irish Bank for a decade up to its nationalisation in 2009.
But in an unprecedented move the accountants are now being sued by the bank for their conduct in the run up the financial crisis.
The case relates solely to what were described in court as the bed and breakfast transactions of former chairman Sean Fitzpatrick over a number of years.
This relates to an allegation that loans were temporarily transferred to Irish Nationwide Building Society at the end of the financial year so they would not appear on Anglo's accounts.
Today Senior Counsel Maurice Collins for IBRC said a very substantial sum is claimed by the bank - in excess of €50m euros.
The case has been fast tracked to the Commercial Court and is in again for mention next May.