The European Commission is expected to publish the findings from its two-year investigation into whether Spain's top football teams were given millions of euros in state aid.
It is focused on seven teams, including rivals Barcelona and Real Madrid - as well as Athletic Bilbao, Osasuna, Valencia, Elche and Hercules who play in Spain's second tier.
The EU is concerned that football clubs have been offered unfair tax breaks, property deals and loan agreements.
The Commission is expected to find against the Spanish state according to a number of reports. This could lead to some belt-tightening in Spain.
When the inquiry was opened in late 2013 EU authorities said, "Professional football clubs should finance their running costs and investments with sound financial management rather than at the expense of the taxpayer.
"Member states and public authorities must comply with EU rules on state aid in this sector as in all economic sectors."
The investigation is focused on three elements:
- Possible corporate tax privileges being given to Real Madrid, Barcelona, Athletic Bilbao, and Osasuna since 1990.
- A complex land deal struck between Real Madrid and local authorities - a negative finding could cost the club €18m.
- There is also an investigation focused on the legality of loan guarantees given to Valencia, Hercules, and Elche by the state-owned Institute of Finance when these clubs faced financial difficulties.
The Commission is also investigating state aid allegations in The Netherlands - this involved five clubs, but The Financial Times reports that there will be no negative findings.
