UEFA on Friday fined both Manchester City and Paris Saint-Germain 60 million euros ($90 million) and capped their Champions League squad to 21 for falling foul of financial fair play rules.
Newly-crowned English Premier League champions Manchester City enjoyed a massive spending spree under billionaire owner Sheikh Mansour bin Zayed al-Nahyan of Abu Dhabi.
And French Ligue 1 champions PSG have benefited from similar investment in top-drawer players after their takeover by Qatar Sports Investments in late 2012.
But both clubs have paid for that with massive fines, 40 million euros of which will be repaid should the clubs fulfil the "operational and financial measures agreed with the UEFA CFCB (Club Financial Control Body)".
UEFA said other clubs to have failed the financial fairplay rules were Turkish trio Buraspor, Galatasaray and Trabzonspor, Russian sides Zenit St Petersburg, Anzhi Makhachkala and Rubin Kazan, and Levski Sofia from Bulgaria.
City battled UEFA through to the end, saying there had been "a fundamental disagreement" over the interpretation of the FFP regulations on players purchased before 2010 but that it had "decided to enter into a compromise agreement with UEFA".
They agreed, the statement read, to limit their net spending on new players to 60 million euros.
And the wage bill of the whole club (playing and non-playing staff) for 2014-15 will need to remain at the same level as that of 2013-14 season.
UEFA's Investigatory Chamber, which led the inquiry, has powers to impose sanctions, including heavy fines and a wage cap on the squads to appear in next season's Champions League.
The sanctions package is understood to be part of a settlement offer to the clubs, which they can accept or reject or try to reach an amicable settlement.
The sanctions are designed to restrict expenditure on players by clubs who have breached the rules and help them in their efforts to comply with the limits on losses in future seasons.
The ruling came after a week of uncertainty over the timing of the announcement and marked by the sudden death of the man who led the investigation as head of the CFCB, former Belgian prime minister Jean-Luc Dehaene, on Thursday.
Dehaene, 73, had been diagnosed with cancer earlier this year but died after a fall in France.