A breach of the AFL's player payment rules has cost Adelaide a $20,000 fine.

Half the fine is suspended until October 31 next year and the AFL says the penalty relates to "arrangements between a player and associates of the club".

Adelaide football manager John Reid said the un-named player, who does not have a manager, did not inform the Crows of the financial agreement.

He said the Crows had told their players repeatedly that they must let the club know about employment or marketing agreements with sponsors or other supporters, such as coterie group members.

"This player has entered into an agreement, we weren't aware of it and unfortunately we got fined," Reid said.

"It was a communications thing ... there was no impropriety on the part of the club, but we've got to wear it, that's the rules."

In a statement, the league said Adelaide had voluntarily disclosed the breaches as soon as they were discovered.

"The AFL's Investigations Manager Ken Wood found that the club had failed to lodge arrangements between a player and associates of the club within the required timeframes, as required by the Total Player Payment (TPP) rules," the league added.

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