The number of clubs suspected of rule breaches has fallen from 76 after further investigations since February.
European football's governing body will not disclose the identity of the clubs involved and whether any are English.
Arsenal, Chelsea and Manchester United have told Sky Sports News they are not under investigation.
And it is understood Manchester City do not believe they are in breach of rules after deductions for infastructure, youth and community spending. It is believed they expect to break even at the end of this season.
UEFA's independent club financial control body (CFCB) will meet on Tuesday for two days in Nyon, Switzerland and discuss further action for clubs that fail to meet its financial requirements.
The CFCB is made up of two chambers, one investigative and the other adjudicatory.
Former Celtic chairman Brian Quinn is one of eight officials on UEFA's Investigatory Chamber.
Charles Flint QC, an English barrister, is one of five officials on UEFA's Adjudicatory Chamber.
UEFA has not yet disclosed the punishment for clubs that fail its rules but it can impose a number of sanctions including a warning, fine, disqualifying clubs from its competitions, including the Champions League and Europa League, and withdrawing a title or award.
Under rules since 2011, European clubs can spend up to £4m (€5m) more than they earn per year but can exceed this level to a certain limit until the end of the 2017/18 season.
Clubs can spend around £37m (€45m) more than they earn until the end of next season - if it is entirely covered by a direct contribution from the club owner or a related party.
Between 2015 and 2018, clubs will only be allowed to spend around £25m (€30m) more than they earn under the same limits.
UEFA says financial fair play is "about improving the overall financial health of European club football."