Lauren Cranston, the daughter of a former deputy commissioner of the ATO, has been found guilty of her role in a $105 million tax-fraud conspiracy.
Both Lauren Cranston, and her brother, Adam, were among five people to face a trial in the NSW Supreme Court, which began last April.
The court heard allegations of a long-running scam in which the accused parties ripped off the government by keeping more than $100 million in GST and Pay As You Go (PAYG) tax.
It was alleged a legitimate payroll company called Plutus Payroll was used to collect gross wages from employers, before money that should have gone to the ATO was siphoned off into "second tier" companies to distance the defendants from the fraud.
It was the Crown case that random, unconnected and sometimes vulnerable parties were installed as directors of those companies.
Last week, the jury found Adam Cranston and co-accused Dev Menon and Jason Onley guilty of conspiring to dishonestly cause a loss to the Commonwealth and conspiring to deal with the proceeds of crime.
Ms Cranston was on Monday found guilty of the same two charges.
She began sobbing as the result was announced in court.
The jury has not yet reached a verdict in relation to the fifth defendant, Patrick Wilmott.
The Cranstons are the children of former ATO deputy commissioner Michael Cranston.
There is no suggestion Michael Cranston was involved in wrongdoing.
The jury was told Plutus proudly boasted a zero-fee service, but the Crown said it was "too good to be true".
The court heard hundreds of recorded conversations, including a phone exchange from April 2017 which the prosecution pointed to as being highly instructive.
In that recording, Adam Cranston said to Menon that if it was uncovered "it would be f****n' Ben Hur man, this is a big size company".
Menon replied: "It would be the biggest tax fraud in Australia's history, definitely, there is no question. It would be the biggest tax fraud."
The court heard that by July 2016, "alarms" had started to go off at the ATO, and a covert operation was running.
The alleged multi-million-dollar scam was uncovered by the Australian Federal Police with assistance from the ATO in 2017 as part of Operation Elbrus.
After Monday's verdict was returned, Justice Anthony Payne sent the jurors home for the day before they return to deliberations in the morning.
"Thank you for your continued outstanding dedication to the case," the judge said.
