Clearance services ensure trades made between buyers and sellers of shares "settle" by essentially overseeing the back office administration behind the transactions.
In addition to concerns about so-called pay-to-play practices, they have questions about the use of soft-dollar arrangements, in which brokers collect higher commissions on trades in return for providing research and other services to advisors.
The taxpayer must perform more than 750 hours of services during the year in real property trades or businesses in which the taxpayer materially participates.
For Italy, it is the latest in a string of corporate scandals - including risky trades at the bank Monti Paschi di Siena and allegations of bribery at the oil services group Saipem.