Allied Irish Banks has suffered a second technical issue in as many days, disrupting services for customers.
The bank said its systems were affected for less than 30 minutes this morning, but were quickly back up and running less than 24 hours after the first interruption.
"Everything is working normally," a spokeswoman for AIB said.
The state-owned bank's mobile services were offline for several hours yesterday, with customers advised to use branches, ATMs or internet services.
AIB has more than one million users of its online services and also suffered IT issues late last month which disrupted internet and tablet banking.