Anderlecht have been fined €5,000 (£4,315) by the Belgian FA for naming Vincent Kompany as head coach without the required qualifications.
Kompany was appointed player-coach in May in a bid to revive the ailing fortunes of the country's most successful team.
But Belgium requires all head coaches of top-flight clubs to hold a UEFA Pro licence, which the former Manchester City player does not have.
The club stated Simon Davies, the Manchester City academy chief who followed Kompany to Brussels in the summer, was actually the head coach.
However, the Belgian FA rejected this claim, using Anderlecht's own media statements and unveiling video clips to refute it and gave the club a strong reprimand for insufficient respect for compliance with the regulations.
"The club violated the regulations for a long time and despite that it being against the rules did not hesitate to publicly unveil a coach without a diploma," the associations licensing committee said in a statement.
Anderlecht have won only two of 10 league games under Kompany and currently lie 13th in the 16-team league.
Anderlecht have since named Frank Vercauteren, who has the necessary qualifications, as head coach, saying he was replacing Davies, who stays on as an assistant coach.
But it has not cleared up who is actually in charge at the club with Anderlecht claiming Vercauteren would be in charge on matchdays, suggesting Kompany was still in overall charge.