The fine includes $15,000 which is suspended for 12 months.

Hayley Silver-Holmes was picked to play against Melbourne Renegades on Saturday night despite not being part of the Sixers' official squad.

The teenage fast bowler was returning from injury and the Sixers had not lodged the correct paperwork to clear her to play.

Silver-Holmes had been replaced in the official squad by Alisha Bates.

Upon realising their error, the Sixers removed Silver-Holmes from Saturday night's match before she had batted or taken the field.

Maddy Darke was named as the 12th fielder and went onto the field in Silver-Holmes' place.

The Sixers self-reported the issue, a fact which was noted by CA senior conduct commissioner Alan Sullivan QC at a hearing on Sunday.

CA said the maximum penalty of $50,000 and further sanctions were not deemed appropriate given the nature of the breach, and the fact Sixers lost the match and adversely impacted their Net Run Rate.

"Cricket Australia places a significant emphasis on the integrity of all competitions, including the compliance with its player contracting rules and regulations," CA head of integrity and security Sean Carroll said.

"This breach by the Sydney Sixers, while serious in nature, had a reduced impact due to the club's actions during last night's game.

"As such, we support the findings of Alan Sullivan QC, including the suspension of $15,000 of the $25,000 fine imposed."

The Sixers accepted their penalty.

"We made a regrettable administrative error for which there are understandably stringent rules," Sixers general manager Jodie Hawkins said.

"We were given a fair opportunity to present our case in the hearing and accept the findings and sanction.

"As a club we will learn from this and put processes in place for the future."

Australian Associated Press