Ulster Bank may be hit with a Central Bank fine of up to €5m for the IT failure that left customers unable to access their bank accounts for weeks on end in the summer of 2012.
An investigation into the issue is underway, a spokeswoman for the Central Bank said.
"The Central Bank has been actively engaged with Ulster Bank in relation to the IT incident which occurred in June 1012.
"We are continuing to progress our investigation and are also working closely with the relevant UK authorities.
"Once that investigation is concluded, the Central Bank will consider what appropriate regulatory action to take. This will include considering our enforcement options," she said.
Last night, Sky News reported that authorities in the UK are set to fine Ulster Bank's parent Royal Bank of Scotland (RBS) "tens of millions of pounds" for the failures, which also hit millions of UK customers.
Irish customers suffered the worst disruptions to their services of any customers when the glitch" hit RBS Group, because of a queuing system within the group's technology infrastructure.
It meant that as problems were repaired, customers in Scotland, England and Wales regained access to their services before Ulster Bank account holders.
A maximum fine of €5m can be levied by the Central Bank on a bank for failures dating back earlier than last year, if an investigation finds grounds to impose a financial penalty.
Changes to the Central Bank's Administrative Sanctions Procedure introduced in 2013 now allow for tougher sanctions including fines of up to €10m.
Ulster Bank declined to comment last night. But last week, in its third quarter financial results, RBS confirmed that the Central Bank of Ireland had commenced enforcement proceedings against Ulster Bank, and that it expected settlement discussions to commence before the end of the year.
Details of those negotiations do not have to be made public but any sanctions imposed on the bank will be published.