An estimated 170,000 AIB account holders have been refunded for being overcharged on certain foreign exchange transactions.
The bank lodged the sum overcharged plus interest into accounts last Friday and letters informing those concerned have been posted and should arrive today and tomorrow.
The bank was unable to say how many more overcharged account holders have yet to be identified. It has requested customers who believe they may have been overcharged to contact their branch.
Up to €25.6 million has been set aside by the bank to repay customers charged fees greater than those notified to the regulator. The rate notified to the regulator was 0.5 per cent, and the amount charged was 1 per cent over a period of eight years.
AIB also intends to repay a further €8.1 million after identifying 24 other cases where the bank had charges in excess of the rate agreed with the customer, bringing the total amount to be repaid to €34.2 million.
The overcharging came to light when a whistleblower contacted RTÉ after becoming frustrated at a perceived lack of response from Irish Financial Services Regulatory Authority, to which the whistleblower had first brought their concerns.
AIB then issued a statement confirming that an "error" had been made in certain foreign exchange transactions on May 6th.
A spokeswoman for the bank said there was as yet no date for the completion of a further report arising from an ongoing investigation dealing with how the overcharging occurred, and how the bank dealt with the issue.