There have been calls this evening for AIB to establish a full redress scheme for individuals who were wrongly moved off tracker mortgages.
Last week the bank said it had set aside €105m for customers who would have to be repaid after they were moved to standard variable loans with higher interest rates.
RTÉ News has seen a letter sent to one customer of the bank in recent days.
In the correspondence the client has been told their mortgage will be reduced by €15,000 because they were overcharged.
However, the letter does not mention compensation - this is in contrast to a similar situation at Permanent TSB, which offered compensation up front.
David Hall, director of the Irish Mortgage Holders Organisation, said AIB should introduce a full redress scheme for customers.
RTÉ News understands that although the bank did not mention compensation in its letter to the mortgage holders it does not mean there will not be further reimbursement at a later stage.
In a statement, AIB said it was undertaking a comprehensive review of the tracker mortgage issue, which will take some time to complete.
It said the process would be verified by the Central Bank and a third party.
It said when the review is completed it will be contacting all affected customers.
However, it said that it may be in contact with some customers during the review.
In a statement, the Central Bank said "the tracker mortgage examination is currently under way and the examination requires lenders to carry out a review in order to identify customers who have been negatively impacted and, where there has been detriment, to provide redress."