St George branches have been thrown back 50 years after a technical fault blacked-out tellers across Sydney and forced operators to fill out manual receipts.
The fault meant operators could not access its Spider teller system, reportedly since 9am this morning.
An operator within a Sydney St George Bank branch said the systems were knocked out across the city and staff are resorting to pen and paper until the as-yet unknown fault is resolved.
A spokesman for the bank confirmed the outage but said other information was yet to be confirmed.
He said he understands the fault had lasted an hour and is presently being resolved.
Westpac, which acquired St George in 2008, has remained unaffected.
Chief executive officer, Gail Kelly, said last year Westpac would consider adopting the Spider teller system, along with its customer relationship management system, Firefly, and its HR portal, HR Express.
Each of the big four banks have endured IT-related outages, however Westpac had blamed staff for botched payments which caused thousands of customers to miss payments, be overcharged and overpaid in 2008.