Several National Australia Bank staff took cash from "introducers" such as a gym owner and tailor for loans that some customers could not afford, an inquiry has heard.
There were also cases of bankers accepting payment from customers for loan approvals, the financial services royal commission heard.
Four people, including the gym owner and tailor, brought in $139 million in loans for NAB over four years, together earning $630,000 in commissions.
The bulk of that amount - $488,000 - was paid to one introducer, documents before the royal commission show.
The inquiry heard 60 bankers including branch managers were involved in fraud and misconduct connected to NAB's introducer program, which pays people outside the bank such as financial planners and accountants for successful lending referrals.
Several bankers created false documents and accepted cash payments from introducers, a January 2016 NAB document said.
A KPMG investigation found some bankers were helping customers prepare false pay slips while some customers living in Australia claimed to be full-time employees in China.
By early 2016 NAB had identified six customers with $3.5 million of loans in arrears and 90 with $50 million in loans where there were concerns over their ability to service the debt.
Senior counsel assisting the commission Rowena Orr QC said many customers ended up with loans they should not have had and were not able to afford.
Senior NAB executive Anthony Waldron said there were some obvious cases where that occurred.
The bank believes 1360 customers have potentially been impacted by the fraud and misconduct.
A small number of those are expected to be offered remediation soon.
"We have identified that there would be about 26 of those that we would be making offers to over the next little while, over the next week or two," Mr Waldron said.