Porto and Sporting CP face a one-year ban from playing in Europe if they fail to pay outstanding debts by the end of next month.
UEFA on Friday revealed sanctions that have been issued to eight clubs for breaches of Financial Fair Play (FFP) regulations.
Primeira Liga leaders Porto and second-placed Sporting have been fined €300,000 and €250,000 respectively and will not play in the next UEFA club competition they qualify for in one of the next three seasons unless they can prove by January 31, 2022 they have settled "outstanding overdue amounts."
LaLiga side Real Betis have been hit with a €250,000 fine, while CSKA Sofia and CD Santa Clara were both ordered to pay €75,000 and Mons Calpe SC must fork out €15,000.
All of those clubs also face missing out on playing in Europe in either the 2022-23, 2023-24 or 2024-25 season if they qualify, but have not paid what they owe.
FC Astana and CFR 1907 Cluj were fined €150,000 and €200,000 respectively, but were not threatened with a ban.
The newly established First Chamber of the UEFA Club Financial Control Body (CFCB First Chamber) also found that AEK Athens did not comply with several club licensing and FFP rules.
The Greek club agreed to pay an unconditional financial contribution of €1.5million, while they will also withhold 10 per cent of UEFA prize money they make in the next UEFA club competition they qualify for.