A store owner in South Australia's remote APY Lands has been fined $167,500 for withdrawing almost $1 million from the accounts of local residents.

The Federal Court previously found the owner of Nobby's Mintabie General Store, Lindsay Gordon Kobelt, had withdrawn the money from the accounts of 85 customers between July 2010 and November 2012.

It was told Kobelt used an informal credit system known as 'book-up' that allows people to buy goods on the spot and pay later by providing their account information.

Nobby's also sold cars and customers had used the book-up arrangement for purchase of second-hand vehicles.

Kobelt had each customer's bank debit card and PIN details and used EFTPOS machines to access the accounts, withdrawing wages or Centrelink benefits about the time they went into the accounts.

Corporate regulator ASIC found Kobelt failed to keep good records of what customers owed him and made deductions well in excess of what people had spent.

The Federal Court found him guilty late last year of unconscionable and unlicensed conduct, finding Kobelt was indifferent and defiant to his obligations under the National Consumer Protection Act.

It heard he described a fact sheet ASIC provided about his obligations as "bullshit" after reading the first few lines.

Penalty could have had 'crushing effect'

In his judgment, Justice White said he would reduce the total penalty from $230,000 so it did not have a "crushing effect" on the store owner.

"It is particularly pertinent that he is a 73-year-old sole trader and will bear personally the burden of the court's penalties," he said.

"There is the prospect that the penalties outlined above will have a crushing effect, taking into account his financial situation."

ASIC deputy chairman Peter Kell said the penalty was a warning to those in the credit industry that exploitation of financially vulnerable consumers would have serious consequences.

"ASIC is continuing to work with book-up providers and Indigenous communities to ensure that all consumers are treated fairly," he said.

"Behaviour that is unscrupulous or illegal will not be tolerated."

Payment of the penalty will now depend on the outcome of an appeal Kobelt has lodged against the Federal Court's finding of misconduct.