The fraudulent transfer slips were used to transfer $10,000 of Aesha's money into a separate account, which the caregiver would later withdraw from an ATM, using Aesha's EFTPOS card.
The case was investigated by dispute resolution service Financial Services Complaints Limited (FSCL) after the offending had been discovered by a bank teller who noticed the altered withdrawal slip and alerted the police.
The charity group laid a complaint with the FSCL believing that the credit union should have done more to prevent the fraudulent withdrawals.
Susan Taylor, FSCL chief executive, said extra care needed to be taken by financial institutions when dealing with vulnerable consumers.
"Vulnerable consumers often require a higher level of assistance from the financial institutions they deal with because they can have greater needs, so extra effort and care on the part of financial institutions will often be necessary," Taylor said.
Taylor added that the development of the Conduct of Financial Institutions legislative framework in the near future would likely increase fair conduct obligations on non-bank deposit takers.
"This means the obligations on financial institutions in relation to their treatment of vulnerable consumers are likely to increase. It may be worthwhile reviewing policies and procedures now to see where services may be able to be improved," she said.
During the FSCL's investigation, the charity argued it was clear the withdrawal slips had been altered, and that there should have been a $100 withdrawal limit on Aesha's account.
The charity added that transfers to the ATM account were not authorised at all.
The credit union disputed it was liable, claiming that Aesha signing the withdrawal slip in front of the teller was sufficient and that the charity, or Aesha's family, should have picked up the large withdrawals on regular bank statements.
The FSCL found that although the charity had not explicitly asked for a credit limit to be put on the amount that could be withdrawn, the credit union had relaxed the "two-to-sign" measure by allowing the withdrawal slip to be signed by one signatory off-site, a factor that contributed to the fraud being able to take place.
The disputes service also considered that the credit union's staff should have noticed the obvious altering to the withdrawal slips and that the number of ATM withdrawals, unusual for Aesha who had not used ATMs previously, had spiked.
The FSCL asked the credit union to reimburse 40 per cent of the amount stolen, which both parties agreed to.