Man City are facing probes by Uefa, Fifa and the Premier League after series of allegations regarding breaches of rules relating to Financial Fair Play, third party ownership and the transfer of underage players.
The club have robustly denied any wrong-doing, while manager Pep Guardiola has pleaded for a swift resolution so focus can return to his side's remarkable achievements on the pitch.
Here Standard Sport assess the allegations and probes into the Premier League champions and what it means for the future of the club that changed the face of European football when falling under Abu Dhabi rule more than 10 years ago.
What are the allegations?
City have been the subject of a series of claims based on leaked documents and emails obtained by the whistle-blower Football Leaks.
The club were rocked by a succession of articles published by German outlet Der Spiegel, which reported claims that City devised numerous methods of disguising the vast sums of investment from their Abu Dhabi owners in order to avoid FFP penalties.
It is claimed they artificially inflated sponsorship, with a £67.5m deal with Etihad alleged to have included £59.5m-worth of investment from the Sheikh Mansour - owned Abu Dhabi United Group.
Other allegations detailed a secret project dubbed 'Longbow,' which involved selling off image rights to a company alleged to be funded by the same group.
In one potentially damning email, City's chief financial officer Jorge Chumillas is claimed to have outlined the need to make up the cost of paying off former manager Roberto Mancini.
Der Spiegel reported the email said:
"We will have a shortfall of £9.9m in order to comply with UEFA FFP this season," he's alleged to have written. "The deficit is due to RM termination. I think that the only solution left would be an additional amount of AD sponsorship revenues that covers this gap."
AD is believed to refer to Abu Dhabi.
It is also claimed in recent weeks that City paid the agent of Jadon Sancho £200,000 when the then 14-year-old signed from Watford.
Players cannot be represented by agents until the year they turn 16.
A separate allegation reported by Danish newspaper Politiken regards a potential breach of third party ownership rules.
It claimed City had a deal with Danish club FC Nordsjaelland president Tom Vernon to sign talent from his African football academy for free.
Third party ownership has been banned since 2015.
In 2017 Fifa launched an investigation into City's recruitment of young players.
What are the potential punishments?
They are wide-ranging, depending on the nature of the offense and which governing body is administering the penalty.
City were already hit with a £49m fine, transfer cap and reduced playing squad in the Champions League when previously found in breach of FFP rules in 2014.
They were also fined £300,000 and banned from signing academy players from rival Premier League or EFL clubs for two years in 2017 when found guilty of making illegal approaches.
If found guilty of any of the latest allegations they could face further fines, Champions League expulsion and transfer bans.
Among the less punitive actions is the possibility of a 'rehabilitative approach' in which City would be offered a 'roadmap' to reach break-even.
Barcelona, Real Madrid, Atletico Madrid and Chelsea have all been handed transfer bans in recent times regarding the signing of minors.
What is FFP?
According to UEFA "Financial Fair Play is about improving the overall financial health of European club football."
European football's governing body devised the system with the intention of ensuring clubs were sustainable and avoided irresponsible ownership by avoiding overspending.
Who is irresponsible?
City fans would argue their mega-rich owners have the right to spend whatever they wish on the club.
Sheikh Mansour certainly has the money to hand Guardiola half a billion pounds to construct his all-conquering squad – and after more than a decade of ownership there is little doubt he is in it for the long haul.
But there are enough examples of other clubs that have spent beyond their means and left on the brink of ruin.
Uefa insist they want all clubs to spend in relation to what they generate to ensure a more sustainable model.
City's recently published accounts that suggest they do just that.
They recorded revenues of £500.5m, which represented a 44 percent increase in five years and a fourth straight year of profitability.
Doesn't FFP just ensure the rich get richer?
That's what it's critics would say. That it creates a closed shop for the established clubs in European football – and stamps out the ambition of those who want to break into it.
Others claim it prevents prospective owners from playing fast and loose with clubs with generations of heritage that can be wiped out the moment the money runs out.
What do City say?
They had previously refused to comment on the specific allegations made by Football Leaks, saying: "The attempt to damage the club's reputation is organised and clear."
After Uefa's confirmation that they had launched an investigation City issued a robust statement:
"Manchester City welcomes the opening of a formal Uefa investigation as an opportunity to bring to an end the speculation resulting from the illegal hacking and out of context publication of City emails.
"The accusation of financial irregularities are entirely false. The Club's published accounts are full and complete and a matter of legal and regulatory record."
What does Guardiola say?
The Catalan says he has been given assurances that the club have acted properly.
"The club is open so hopefully it can finish as soon as possible and Uefa can decide what he sees," he said. "I said last season, I trust a lot what the club has done because I know them, but hopefully they can solve it as soon as possible and stop for this environment."
