Ulster Bank has said arrangements are being put in place to help customers who owe them money after they were undercharged on their mortgage repayments.
It emerged today that Ulster Bank undercharged more than 1,000 customers some €30,000 each.
The undercharging happened after people who had arranged to pay interest-only on their mortgages, did not revert to repaying the principal at the time agreed with the bank.
Chief executive of the Consumers Association of Ireland Dermott Jewell said the affected customers will not have to pay additional interest.
"They may offer those people an interest-free loan in order to pay the principal amount that's outstanding, so it won't be attracting further interest," he said.
"In addition, they will extend the period if necessary beyond the initial term of the mortgage."