National Australia Bank paid thousands of people about $100 million in commissions to "introduce" potential customers to the bank, an inquiry has heard.
At the program's peak NAB had 8000 introducers, people outside the bank who it paid for successful lending referrals.
Senior counsel assisting the financial services royal commission Rowena Orr QC said the introducer program was extremely profitable for NAB during the 2013-2016 period when misconduct occurred, bringing in more than $24 billion in home loans.
Commissioner Kenneth Hayne QC said the bank paid out about $100 million in commissions during that time, when all the introducer was to tell a would-be borrower was that NAB was a bank.
Senior NAB executive Anthony Waldron said they would provide that information and pass the contact details to the bank so it could start a discussion with the customer about their lending requirements.
Asked by Mr Hayne if that was worth the bank outlaying $100 million, Mr Waldron said: "We believe so, in terms of the value of the mortgages that were put on the books."
Ms Orr said in the misconduct cases, there were numerous examples of introducers providing the customer's loan documentation to NAB.
The introducers are financial planners, accountants, property developers, solicitors, builders or architects.
But the inquiry heard the introducers involved in the cases of misconduct fell outside those industries, including people who ran gyms.
"We weren't as strict on ensuring they came from just those industries that we felt comfortable with during that period of time," Mr Waldron said.
The commission heard a whistleblower told NAB in 2015 about a syndicate of 11 NAB employees taking $2800 bribes for fraudulent home loans with the money exchanged in white envelopes passed over the counter.
Ms Orr said 60 bankers including branch managers were involved in varied levels of misconduct connected to the introducer program, 20 of whom were sacked or resigned.
Mr Waldron, NAB's executive general manager of broker relationships, will continue his evidence on Wednesday.