A glitch saw thousands of Bank of Ireland customers were allowed to withdraw large sums from cash machines despite having little or no money in their accounts.
Videos circulating on social media showed long queues at ATMs in various cities, as well as police guarding some cash points.
The technical faults which lasted for several hours on Tuesday were resolved by Wednesday morning.
A spokesperson from the bank said: “We are aware that the technical issue meant some customers were able to withdraw or transfer funds above their normal limits. These transfers and withdrawals will be applied to customers’ accounts today.”
“We urge any customer who may find themselves in financial difficulty due to overdrawing on their account to contact us.”