Atletico Madrid will not be able to register any new players until January 2018 after the Court of Arbitration for Sport upheld their appeal against a FIFA transfer ban.
Atletico, along with city rivals Real Madrid, were handed two-window transfer bans in January 2016 for multiple breaches of global football's rules on the registration of under-18s and both clubs failed in their appeals to FIFA last September.
The two Spanish giants then took their cases to the CAS but, while Real saw their ban halved to one transfer window in December, Atletico announced on Thursday that the only reduction they had been given was regarding their financial penalty - down from £720,000 to £440,000.
A club statement read: "CAS maintains the prohibition to register players until January of 2018.
"They partially upheld the appeal presented by Atletico de Madrid, reducing the financial penalty but maintaining the prohibition of registering licenses this summer."