A bookmaker who claims to have taken a $5 million bet on Lonhro's last race has answered sceptics who doubt the veracity of the wager and say it was a publicity stunt for his Darwin-based firm.

Michael Sullivan has revealed his official ledger, which the Tax Office audits.

It does not reveal the punter's identity but it at least means he'll have to pay $500,000 GST and $20,000 turnover tax.

Sullivan and his mystery punter have been front and back page news across the country, and broadcast just as widely on radio and television, since the first of three million-dollar bets were reported on March 5.

The punter is supposed to have lost $5 million on the stallion at Sydney's Randwick racetrack on Saturday in the Queen Elizabeth Stakes when Lonhro ran second to Grand Armee.

But Sullivan says the punter has been successful on Lonhro with bets of $1 million in the Australian Cup on March 8 and $2 million in the George Ryder Stakes on April 3.

"If this was a publicity stunt, it was a very expensive one," Sullivan told the Daily Telegraph newspaper.

" ...If I was looking for publicity, it's cheaper to take out an ad."

Details of the punter's identity have conflicted, with some saying he is an Australian businessman holidaying overseas or living in Hong Kong or is a European-based businessman.

Inquiries by The Australian newspaper with professional punters and bookmakers in Darwin, Macau, Hong Kong and London have failed to shed any light on the identity of the punter.

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