UEFA on Friday fined both Manchester City and Paris Saint-Germain 60 million euros (82 million dollars, 49 million pounds) 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 benefitted 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.
Both City and PSG battled UEFA through to the end, the former arguing 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.
"The club's expenditure on new players for the upcoming summer transfer window, on top of income from players it might sell, will be limited to 60m euros. This will have no material impact on the club's planned transfer activity," City said.
"The MCFC Champions League squad for the 2014-15 competition will be limited to 21 players. In 2013-14 the club registered 23 players for the competition and used 21.
"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.
PSG said: "After due reflection, Paris Saint-Germain has taken the decision to accept the measures imposed on it in spite of the tremendous handicap they represent in terms of the club's ability to fully compete on an equal footing against Europe's biggest teams."
PSG president Nasser al-Khelaifi added: "Our ambition to build one of the best and most competitive European football clubs will not be undermined by these measures.
"In pursuing this ambition, all our teams will continue to work even more with all their talent and energy to increase the club's revenues around the world and build the Paris Saint-Germain into one of the leading global sport brands.
"We will continue to invest in developing a highly competitive team and will continue our investments in our stadium and training infrastructures while at the same time remaining, as we are today 'debt free'."
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.
- Sudden death -
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.
But if a club refuses to comply with the Chamber's ruling, their case would go to a tribunal which would rule on the matter in June.
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.
UEFA general secretary Gianni Infantino said on Tuesday at an Executive Committee meeting in Turin, Italy, that delays in announcing punishments for breaches of Financial Fair Play were 'normal'.
"The procedure is clear and is following its course. It is a normal delay due to legal procedures," said Infantino.
"If the decisions have not been taken when the media expected them to be, then it is simply because the procedure is not finished."
The announcement had been expected several days earlier.