Chelsea have been banned from signing players in the next two transfer windows by FIFA.
The ban is in relation to rules broken by the club over the signings of 29 foreign players aged under 18.
The ban is subject to appeal but should it stand then Chelsea would be unable to register players until the summer of 2020.
FIFA have issued Chelsea with a £460,000 fine and issued the following statement.
'The FIFA Disciplinary Committee has sanctioned the English club Chelsea FC and The Football Association for breaches relating to the international transfer and registration of players under the age of 18,' a statement read.
'Chelsea was found to have breached art. 19 of the Regulations in the case of twenty-nine (29) minor players and to have committed several other infringements relating to registration requirements for players. The club also breached art. 18bis of the Regulations in connection with two agreements it concluded concerning minors and which allowed it to influence other clubs in transfer-related matters.
'The Disciplinary Committee sanctioned Chelsea with a ban on registering new players at both national and international level for the next two (2) complete and consecutive registration periods. This ban applies to the club as a whole - with the exception of the women's and futsal teams - and does not prevent the release of players.
'Additionally, the club was fined CHF 600,000 and given a period of 90 days to regularise the situation of the minor players concerned.
'The Football Association was also found to have breached the rules in connection with minors. It was fined CHF 510,000 and given a period of six months to address the situation concerning the international transfer and first registration of minors in football.
'The protection of minors is a key element in FIFA's overall regulatory framework relating to the transfer of players and effective enforcement of these rules is paramount, as also confirmed on various occasions by the Court of Arbitration for Sport.
'The decisions issued by the Disciplinary Committee were notified today and can be contested before the FIFA Appeal Committee.'
The ban, which does not prevent the 'release' of players is likely to have huge implications on the club's immediate future.
Christian Pulisic was signed from Dortmund in January and arrives at the end of the season in a £57million deal.
However, the biggest complication could be over Eden Hazard.
The Belgian has less than 18 months to run on his contract at Stamford Bridge and is believed to be keen on a move to Real Madrid.
But, should Chelsea be unable to sign a replacement, they could be forced into allowing Hazard to run his contract down.
The same stands for Callum Hudson-Odoi, who handed in a transfer request in January in a bid to force through a move to Bayern Munich.
The FA have also been fined £390,000 as a result of the club's breaching of FIFA's rules.