The EBS has launched an investigation into a new overcharging blunder involving customers paying for bundled insurance products on their mortgage.
The investigation is understood to be at an early stage and it is not clear how many customers may have been affected. However, sources said a sample of cases suggests the amounts of redress involved are in the "tens to low hundreds of euro".
The overcharging is believed to have occurred on payments for building and life insurance, and mortgage protection insurance products, which are charged directly to the customer and bundled together into the monthly mortgage repayment.
A sample of cases investigated involved customers still paying on their mortgage for insurance products that had closed.
The EBS has around 100,000 mortgage borrowers and a comprehensive audit of all customers who pay for insurance products in this way will have to be conducted.
The investigation was first reported by yesterday's Irish Examiner.
In a statement, the EBS said: "As in any financial organisation, legacy issues will occasionally arise. Our policy, in so far as we can, is to tell our customers first and put things right in the most simple and efficient way possible."
The overcharging will be embarrassing for the financial institution, which is part of the Government-owned AIB, as it comes in the wake of the tracker mortgage scandal.
An investigation by the Central Bank found that more than 40,000 customers were affected when Irish banks withdrew their right to tracker mortgages.