Bank accidentally gives woman AU$25 million

A Sydney woman has been forced to return AU$25 million (NZ$27 million) erroneously deposited in her account.

Lawyer Claire Wainright discovered she was an accidental millionaire after NAB bank deposited almost AU$25 million into her account.

Ms Wainright jokingly posted to Facebook asking her friends if she should simply take the money and leave.

"When NAB accidently pays out your entire mortgage and gives you an extra $24.5 mil to redraw," she said.

"Do I skip the country?"

The error occurred after Ms Wainright set up a direct debit to NAB to pay off her home loan, with the next payment due on October 25.

Instead of withdrawing the payment, her main bank, St George, accidentally paid NAB almost AU$25 million, enough to pay off her entire mortgage several times over.

While it would be tempting for Ms Wainright to take the money, it is illegal to abscond with money accidentally gifted to the bank.

If Ms Wainright were to spend any of the money, she could be charged with theft.

The Financial Ombudsman Service Australia (FOSA) says a mistaken bank payment can put account holders at significant legal risk.

"If money is incorrectly transferred into your account, you should notify your bank. Your bank will then try to return the money to the sender," FOSA advises on its website.

"You should not spend or withdraw the money transferred into your account by mistake because it is not legally yours and you have to pay it back."

Ms Wainright contacted NAB and the money has now been returned to the bank.