Commonwealth Bank of Australia managed to restore service to its online banking system nearly six hours after a "technical glitch" took it down on Monday afternoon.
As a result of the online banking system going down, customers were unable to log on to their NetBank or CommBank banking app.
The bank's ATMs or point of sale systems, however, were unaffected.
A CBA spokesperson told ZDNet technical issues were to blame for the disruption, something which it is still investigating.
"A technical glitch occurred which resulted in customers being unable to log in to our online banking service," the spokesperson said.
"We are currently embarking on a full investigation to understand the root cause of the issue and the full impact. We regret this incident occurred and we apologise to our customers."
This is not the first time CBA has experienced outage issues. In 2014, then-group executive and chief information officer Michael Harte revealed the company had previously frequently experienced 700 outages per year. However, since the company undertook its AU$580 million modernisation project it was able to reduce that number down to two.
More recently in June, CBA was among a handful of other banks that suffered some issues relating to an Eftpos provider, which prevented customers from paying for their shopping at checkout.