Hull FC have accepted the fine of ?5,000 (?4,000 of which has been suspended) imposed by the RFL for a minor breach of the salary cap during the 2005 season.
The club have co-operated fully with the RFL in their investigation and have always offered transparency.
Hull FC chief executive David Plummer said: "The board are determined to give our coaching staff the maximum opportunity to be successful while working as closely to the salary cap as possible.
"Unfortunately it is possible to inadvertantly exceed that limit."
A similar fine was also issued to St Helens, while Wakefield and Castleford were each issued formal written warnings. The Superleague salary cap limits spending on salaries to no more than 50% of the club's "salary cap relevant income" or an upper limit of ?1.7m.