A standard infrastructure upgrade scheduled for Saturday night left Teachers Credit Union members without internet banking for part of yesterday.
Banking services appeared intermittent for users on Sunday and remained down on Monday, relegating users to phone support.
The outage appeared to be fixed at around 1pm AEST on Monday.
Staff confirmed to iTnews that a scheduled infrastructure upgrade had caused the outage.
A spokeswoman said the outage came as the result of a "planned system upgrade" on Saturday night and had been fixed with "some tweaking" on Monday.
The outage comes as the credit union begins its search for a formal chief information officer to oversee IT operations and project management.
The successful applicant would lead the instutition's IT department and project management team.
They would replace current IT manager Colin Thomas, who has driven technology at the company with an IT team of 22 since 2005. He is expected to finish work in January.
It is expected the new CIO would lead the union's continued moves to in-source much of its infrastructure, which was previously outsourced to several vendors.
Over the past several years, Teachers Credit Union has expanded its IBM analytics suite, implemented EMC storage and more recently implemented a unified communications for a 126-seat call centre.
"A key aspect of this role will also be to negotiate contracts with consultants, technical personnel and vendors for products and services in order to maintain the Credit Union's competitive advantage," a job advertisement for the credit union reads.
A spokeswoman said the credit union had decided on a newly created CIO position in light of its efforts to become a mutual bank, considering it an "appropriate time to expand that role" to include business priorities.
The company will seek shareholder approval this month for the change to become a mutual bank.
The bank claims to be the country's third largest credit union and currently provides banking services to 160,000 members in New South Wales, Western Australia, the Australian Capital Territory and Northern Territory.