On the opening day of the League One season, 8th of August, midfielder Emmanuel Osadebe played 89 minutes in Gillingham's 4-0 victory against Sheffield United.
However, it was later discovered that the 19-year-old was not legible to play due to there being an error in his documentation when he registered with the Football League and the Football Association.
Gillingham will have to pay a fine of £4,000 and the club has admitted that Osadebe should not have been selected to play.