At least six Premier League clubs must sell players by June 30, in order to comply with the Profit and Sustainability Rules (PSR).
The date is the cut-off point for the financial year across the English top flight.
Clubs must produce documents that they have made losses of no more than £105m over the last three years.
Chelsea, Aston Villa, Newcastle, Everton, Nottingham Forest and Leicester are all under the pressure of losing a key asset or two, according to Sky Sports News.
The transfer window opens June 14 before the cut-off date.
Clubs that are found to have breached spending regulations may be liable for sanctions, including points deductions.