The incorrect witnessing of beneficiary nomination forms could have potentially rendered the final wishes of more than 2500 National Australia Bank customers invalid.
The banking royal commission is examining the case of NAB financial planners failing to correctly witness forms setting out who individuals want to receive their superannuation funds when they die.
The commission heard a NAB financial adviser forged a couple's initials and asked another employee to falsely witness a form where the husband and wife nominated each other as the binding beneficiary of life insurance through their superannuation.
The inquiry was told the adviser admitted it was a mistake, saying he did not realise at the time the customers had not stated the percentage of funds to go to each other and forgot a second person had to witness the nominations.
"I knew at the time what I had done was wrong," he said in an account read to the commission.