Comeback jockey Michelle Payne has been hit with a $1000 fine over a series of mysterious bets on racing, US basketball and English soccer.

Payne is one of three jockeys who pleaded guilty on Tuesday to betting charges resulting from an audit of corporate bookmaking accounts.

Racing Victoria stewards also fined jockeys Anthony Darmanin and Michael Walker $1000 over bets discovered in their name.

Only Walker admitted personally placing any bets.

The largest of the wagers was a $200 multi on Payne's account on the Singapore Airlines Cup into So You Think in a race in Ireland.

But along with a $50 multi bet on So You Think, Miami Heat, Manchester United, Arsenal, Newcastle and Stoke placed at 2am on one day in May 2011, Payne had no recollection of any of them.

"I don't know where I was that night," she told Tuesday's inquiry.

"I don't recall putting on the bets myself, but it's my account, its my responsibility."

Payne admitted to regularly betting on sports, which jockeys are permitted to do under the rules of racing.

Darmanin also had no recollection of placing a multi bet in which the first leg was a rider he'd never heard of winning a jockey challenge at Townsville.

Walker, a New Zealander, admitted outlaying $57 in four bets, including a $1 trifecta on a South Australian race.

His only defence was that he assumed Australian racing rules permitted jockeys to bet on races in which they weren't riding, or to bet on themselves, as they can in New Zealand.

None of the bets in question was successful.