UEFA has opened formal investigations into overspending by Liverpool and Inter Milan and possible breaches of its Financial Fair Play rules.
The former European champions are among seven clubs which qualified for the Champions League or Europa League this season being investigated for "break-even deficits" in the past two financial years.
Monaco and Roma, both former runners-up, are also implicated, and must provide extra financial reports in the next two months, UEFA said on Thursday.
All four clubs are being closely scrutinized on returning to UEFA competitions this season. Inter plays in the second-tier Europa League.
Their finances were not assessed last season when UEFA started punishing clubs for overspending on transfer fees and wages.
Sporting Lisbon, Besiktas and Krasnodar complete the list of seven clubs who face provisional sanctions later this year, such as threats to withhold Champions League prize money.
Liverpool, Roma and Monaco can all expect to earn at least 20 million euros ($25.5 million) from entry payments, results bonuses, and a share of television rights money.
UEFA has also withheld prize money due to five clubs from this season's competition because they have not paid wages, transfer fees or taxes.
The clubs are: Bursaspor, Cluj, Astra Giurgiu, Buducnost Podgorica and Ekranas.
UEFA said 115 clubs, including the 12 named on Thursday, will be monitored throughout the season. The figure also includes nine sanctioned last season.
Manchester City and Paris Saint-Germain were the worst offenders and UEFA ordered each to pay 20 million euros ($25.5 million) fines. They face further fines totaling 40 million euros ($51 million) each for missing financial targets set by UEFA to curb spending.
UEFA allowed wealthy club owners to cover a maximum of 45 million euros ($57.4 million) of losses on their football-related business from 2011-13 with a one-off equity payment.
The FFP rules encourage clubs to spend freely on stadiums, infrastructures projects and youth training without those costs counting in the break-even assessment.