UEFA has revealed that 76 clubs in European competition this season - about one third of the total - are being investigated for possible breaches of its Financial Fair Play (FFP) rules.
The 76 clubs all failed UEFA's break-even calculations for 2012 and have been asked to provide financial information for 2013. Manchester City, Chelsea and French club Paris St Germain are believed to be among the clubs involved.
The clubs will all now have their finances assessed by the Club Financial Control Body to see if the breaches have continued and whether sanctions should apply.
UEFA general secretary Gianni Infantino said: "This figure of 76 clubs is a high figure but it has to be looked at in the perspective of what the end figure will be."
Clubs face a range of sanctions from a warning or a fine up to being forced to play in Europe with a salary cap on the squad, or even being barred from competing and having trophies stripped.