Bank of Ireland said it has identified the cause of a problem which delayed payments into some customer accounts on Friday morning.
It is understood a processing delay is responsible and the bank said it expected the issue to be resolved at some stage today.
The main problem appears to concern credit transfers from other banks but no pension or social welfare payments are believed to be affected.
It is not yet known how long it will take to resolve the issues, nor how many accounts are affected.
“We are aware that payments to some accounts have been delayed this morning. We are working to resolve this and we are providing updates to customers throughout the morning. We apologise for any inconvenience,” said a company spokesman.
The bank experienced similar problems last April when payments to social welfare accounts were delayed.