Police will allege Mr Fitzgerald, during his time as a Seven executive, created at least 700 "false invoices and incidents" and siphoned funds to a number of bank accounts he had created.

He is said to have used the money for superannuation and to buy real estate.

He was taken to Burwood police station where he is expected to be charged with multiple fraud-related offences.

On Wednesday, Detective acting Superintendent Richard Puffet said that, while the exact number of offences was yet to be determined, they would "definitely reflect the magnitude of the criminality."

"If you bite the hand that feeds you, we will come after you," he said, describing the two-year investigation by police as "extremely complex and laborious".

Mr Fitzgerald worked for Seven West Media for more than 15 years. By the end of his time at the company, he was controlling the group's finance and television programming with a budget worth hundreds of millions of dollars.

It was about this time that an audit detected some suspicious transactions, triggering an internal investigation, which was then referred to police.

In April 2016, Seven West was granted a NSW Supreme Court order freezing millions of dollars worth of shares and properties owned by Mr Fitzgerald.

According to court documents from Seven’s legal action against Mr Fitzgerald, he allegedly used some of the proceeds to buy a beachside apartment on Sydney's northern beaches and a house on the NSW Central Coast, for his son and daughter.

It is understood the three-bedroom Dee Why apartment on Clyde Rd was purchased for $649,000 in 2011 and sold for more than $1.1 million in 2016, while the Terrigal property, a four-bedroom house on Ena Street, was purchased in his son's name for $645,000 in March 2013, and sold in October last year for $890,000,

Mr Fitzgerald also allegedly used money obtained through the fraud to pay off the mortgage on his family home in Glenorie, before selling it for $2.6m in 2016.

It was alleged he defrauded the company by creating, approving and paying false invoices to companies he owned and controlled, dating back more than 13 years. Seven West later quantified the alleged fraud at more than $8 million and referred the matter to the police.

Last year, Mr Fitzgerald and Seven West reached a settlement. The money has been repaid to Seven. The 2016 freezing order has now been rescinded.

In an interview with News Corp papers last year, Mr Fitzgerald said he had always argued that the work he had done was "a legitimate service and it didn’t really affect shareholders, because the service had to be done".

In May it was revealed Mr Fitzgerald was working as a bookkeeper, listed as the Parramatta franchisee for Shoebox Bookkeeping, a small business-accounting and tax-advisory service.

In the role, Mr Fitzgerald managed the accounts of small businesses in Sydney's western suburbs.

Seven has declined to comment, given the matter is before the courts.

Shoebox has not responded to questions about Mr Fitzgerald's status as a franchisee, however it removed the web page for Mr Fitzgerald's franchise business on Wednesday.